protocol v12 changes (/recoup split, signature changes) plus database sharding plus O(n^2)=>O(n) worst-case complexity reduction on coin balance checks

17 files changed, 934 insertions, 1400 deletions

diff --git a/src/exchange/Makefile.am b/src/exchange/Makefile.am
index c20378c22..e7688f735 100644
--- a/src/exchange/Makefile.am
+++ b/src/exchange/Makefile.am
@@ -102,6 +102,7 @@ taler_exchange_httpd_SOURCES = \
   taler-exchange-httpd_metrics.c taler-exchange-httpd_metrics.h \
   taler-exchange-httpd_mhd.c taler-exchange-httpd_mhd.h \
   taler-exchange-httpd_recoup.c taler-exchange-httpd_recoup.h \
+  taler-exchange-httpd_recoup-refresh.c taler-exchange-httpd_recoup-refresh.h \
   taler-exchange-httpd_refreshes_reveal.c taler-exchange-httpd_refreshes_reveal.h \
   taler-exchange-httpd_refund.c taler-exchange-httpd_refund.h \
   taler-exchange-httpd_reserves_get.c taler-exchange-httpd_reserves_get.h \
diff --git a/src/exchange/taler-exchange-httpd.c b/src/exchange/taler-exchange-httpd.c
index 0535a54ea..526c93588 100644
--- a/src/exchange/taler-exchange-httpd.c
+++ b/src/exchange/taler-exchange-httpd.c
@@ -42,6 +42,7 @@
 #include "taler-exchange-httpd_metrics.h"
 #include "taler-exchange-httpd_mhd.h"
 #include "taler-exchange-httpd_recoup.h"
+#include "taler-exchange-httpd_recoup-refresh.h"
 #include "taler-exchange-httpd_refreshes_reveal.h"
 #include "taler-exchange-httpd_refund.h"
 #include "taler-exchange-httpd_reserves_get.h"
@@ -257,6 +258,10 @@ handle_post_coins (struct TEH_RequestContext *rc,
       .handler = &TEH_handler_recoup
     },
     {
+      .op = "recoup-refresh",
+      .handler = &TEH_handler_recoup_refresh
+    },
+    {
       .op = "refund",
       .handler = &TEH_handler_refund
     },
diff --git a/src/exchange/taler-exchange-httpd_db.c b/src/exchange/taler-exchange-httpd_db.c
index 388679c38..3600d7931 100644
--- a/src/exchange/taler-exchange-httpd_db.c
+++ b/src/exchange/taler-exchange-httpd_db.c
@@ -30,55 +30,6 @@
 
 
 /**
- * Send a response for a failed request.  The transaction history of the given
- * coin demonstrates that the @a residual value of the coin is below the @a
- * requested contribution of the coin for the operation.  Thus, the exchange
- * refuses the operation.
- *
- * @param connection the connection to send the response to
- * @param coin_pub public key of the coin
- * @param coin_value original value of the coin
- * @param tl transaction history for the coin
- * @param requested how much this coin was supposed to contribute, including fee
- * @param residual remaining value of the coin (after subtracting @a tl)
- * @return a MHD result code
- */
-static MHD_RESULT
-reply_insufficient_funds (
-  struct MHD_Connection *connection,
-  const struct TALER_CoinSpendPublicKeyP *coin_pub,
-  const struct TALER_Amount *coin_value,
-  struct TALER_EXCHANGEDB_TransactionList *tl,
-  const struct TALER_Amount *requested,
-  const struct TALER_Amount *residual)
-{
-  json_t *history;
-
-  history = TEH_RESPONSE_compile_transaction_history (coin_pub,
-                                                      tl);
-  if (NULL == history)
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_EXCHANGE_GENERIC_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS,
-                                       NULL);
-  return TALER_MHD_REPLY_JSON_PACK (
-    connection,
-    MHD_HTTP_CONFLICT,
-    TALER_JSON_pack_ec (TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS),
-    GNUNET_JSON_pack_data_auto ("coin_pub",
-                                coin_pub),
-    TALER_JSON_pack_amount ("original_value",
-                            coin_value),
-    TALER_JSON_pack_amount ("residual_value",
-                            residual),
-    TALER_JSON_pack_amount ("requested_value",
-                            requested),
-    GNUNET_JSON_pack_array_steal ("history",
-                                  history));
-}
-
-
-/**
  * How often should we retry a transaction before giving up
  * (for transactions resulting in serialization/dead locks only).
  *
@@ -91,24 +42,22 @@ reply_insufficient_funds (
 #define MAX_TRANSACTION_COMMIT_RETRIES 100
 
 
-/**
- * Ensure coin is known in the database, and handle conflicts and errors.
- *
- * @param coin the coin to make known
- * @param connection MHD request context
- * @param[out] mhd_ret set to MHD status on error
- * @return transaction status, negative on error (@a mhd_ret will be set in this case)
- */
 enum GNUNET_DB_QueryStatus
 TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
                      struct MHD_Connection *connection,
+                     uint64_t *known_coin_id,
                      MHD_RESULT *mhd_ret)
 {
   enum TALER_EXCHANGEDB_CoinKnownStatus cks;
+  struct TALER_DenominationHash h_denom_pub;
+  struct TALER_AgeHash age_hash;
 
   /* make sure coin is 'known' in database */
   cks = TEH_plugin->ensure_coin_known (TEH_plugin->cls,
-                                       coin);
+                                       coin,
+                                       known_coin_id,
+                                       &h_denom_pub,
+                                       &age_hash);
   switch (cks)
   {
   case TALER_EXCHANGEDB_CKS_ADDED:
@@ -124,250 +73,20 @@ TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
                                     TALER_EC_GENERIC_DB_STORE_FAILED,
                                     NULL);
     return GNUNET_DB_STATUS_HARD_ERROR;
-  case TALER_EXCHANGEDB_CKS_CONFLICT:
-    break;
-  }
-
-  {
-    struct TALER_EXCHANGEDB_TransactionList *tl;
-    enum GNUNET_DB_QueryStatus qs;
-
-    qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                            &coin->coin_pub,
-                                            GNUNET_NO,
-                                            &tl);
-    if (0 > qs)
-    {
-      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-        *mhd_ret = TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_INTERNAL_SERVER_ERROR,
-          TALER_EC_GENERIC_DB_FETCH_FAILED,
-          NULL);
-      return qs;
-    }
-    // FIXME: why do we even return the transaction
-    // history here!? This is a coin with multiple
-    // associated denominations, after all...
-    // => this is probably the wrong call, as this
-    // is NOT about insufficient funds!
-    *mhd_ret
-      = TEH_RESPONSE_reply_coin_insufficient_funds (
-          connection,
-          TALER_EC_EXCHANGE_GENERIC_COIN_CONFLICTING_DENOMINATION_KEY,
-          &coin->coin_pub,
-          tl);
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tl);
-    return GNUNET_DB_STATUS_HARD_ERROR;
-  }
-}
-
-
-/**
- * Called when we actually know that the balance (was) insufficient.
- * Re-does the check (slowly) to compute the full error message for
- * the client.
- *
- * @param connection HTTP connection to report hard errors on
- * @param coin_pub coin to analyze
- * @param coin_value total value of the original coin (by denomination)
- * @param op_cost cost of the current operation (for error reporting)
- * @param check_recoup should we include recoup transactions in the check
- * @param zombie_required additional requirement that the coin must
- *          be a zombie coin, or also hard failure
- * @param[out] mhd_ret set to response status code, on hard error only
- * @return transaction status
- */
-static enum GNUNET_DB_QueryStatus
-check_coin_balance (struct MHD_Connection *connection,
-                    const struct TALER_CoinSpendPublicKeyP *coin_pub,
-                    const struct TALER_Amount *coin_value,
-                    const struct TALER_Amount *op_cost,
-                    bool check_recoup,
-                    bool zombie_required,
-                    MHD_RESULT *mhd_ret)
-{
-  struct TALER_EXCHANGEDB_TransactionList *tl;
-  struct TALER_Amount spent;
-  enum GNUNET_DB_QueryStatus qs;
-
-  /* Start with zero cost, as we already added this melt transaction
-     to the DB, so we will see it again during the queries below. */
-  GNUNET_assert (GNUNET_OK ==
-                 TALER_amount_set_zero (TEH_currency,
-                                        &spent));
-
-  /* get historic transaction costs of this coin, including recoups as
-     we might be a zombie coin */
-  qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                          coin_pub,
-                                          check_recoup,
-                                          &tl);
-  if (0 > qs)
-  {
-    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                             "coin transaction history");
-    return qs;
-  }
-  if (zombie_required)
-  {
-    /* The denomination key is only usable for a melt if this is a true
-       zombie coin, i.e. it was refreshed and the resulting fresh coin was
-       then recouped. Check that this is truly the case. */
-    for (struct TALER_EXCHANGEDB_TransactionList *tp = tl;
-         NULL != tp;
-         tp = tp->next)
-    {
-      if (TALER_EXCHANGEDB_TT_OLD_COIN_RECOUP == tp->type)
-      {
-        zombie_required = false; /* clear flag: was satisfied! */
-        break;
-      }
-    }
-    if (zombie_required)
-    {
-      /* zombie status not satisfied */
-      GNUNET_break_op (0);
-      TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                              tl);
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_EXCHANGE_MELT_COIN_EXPIRED_NO_ZOMBIE,
-                                             NULL);
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-  }
-  if (GNUNET_OK !=
-      TALER_EXCHANGEDB_calculate_transaction_list_totals (tl,
-                                                          &spent,
-                                                          &spent))
-  {
-    GNUNET_break (0);
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tl);
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_EXCHANGE_GENERIC_COIN_HISTORY_COMPUTATION_FAILED,
-                                           NULL);
-    return GNUNET_DB_STATUS_HARD_ERROR;
-  }
-
-  /* Refuse to refresh when the coin's value is insufficient
-     for the cost of all transactions. */
-  if (0 > TALER_amount_cmp (coin_value,
-                            &spent))
-  {
-    struct TALER_Amount coin_residual;
-    struct TALER_Amount spent_already;
-
-    /* First subtract the melt cost from 'spent' to
-       compute the total amount already spent of the coin */
-    GNUNET_assert (0 <=
-                   TALER_amount_subtract (&spent_already,
-                                          &spent,
-                                          op_cost));
-    /* The residual coin value is the original coin value minus
-       what we have spent (before the melt) */
-    GNUNET_assert (0 <=
-                   TALER_amount_subtract (&coin_residual,
-                                          coin_value,
-                                          &spent_already));
-    *mhd_ret = reply_insufficient_funds (
-      connection,
-      coin_pub,
-      coin_value,
-      tl,
-      op_cost,
-      &coin_residual);
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tl);
-    return GNUNET_DB_STATUS_HARD_ERROR;
-  }
-
-  /* This should not happen: The coin has sufficient funds
-     after all!?!? */
-  TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                          tl);
-  return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
-}
-
-
-enum GNUNET_DB_QueryStatus
-TEH_check_coin_balance (struct MHD_Connection *connection,
-                        const struct TALER_CoinSpendPublicKeyP *coin_pub,
-                        const struct TALER_Amount *coin_value,
-                        const struct TALER_Amount *op_cost,
-                        bool check_recoup,
-                        bool zombie_required,
-                        MHD_RESULT *mhd_ret)
-{
-  bool balance_ok = false;
-  bool zombie_ok = false;
-  enum GNUNET_DB_QueryStatus qs;
-
-  qs = TEH_plugin->do_check_coin_balance (TEH_plugin->cls,
-                                          coin_pub,
-                                          coin_value,
-                                          check_recoup,
-                                          zombie_required,
-                                          &balance_ok,
-                                          &zombie_ok);
-  switch (qs)
-  {
-  case GNUNET_DB_STATUS_HARD_ERROR:
-    *mhd_ret = TALER_MHD_reply_with_error (
+  case TALER_EXCHANGEDB_CKS_DENOM_CONFLICT:
+    *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (
       connection,
-      MHD_HTTP_INTERNAL_SERVER_ERROR,
-      TALER_EC_GENERIC_DB_FETCH_FAILED,
-      "check_coin_balance");
-    return qs;
-  case GNUNET_DB_STATUS_SOFT_ERROR:
-    return qs;
-  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-    GNUNET_break (0);
-    *mhd_ret = TALER_MHD_reply_with_error (
-      connection,
-      MHD_HTTP_INTERNAL_SERVER_ERROR,
-      TALER_EC_GENERIC_DB_FETCH_FAILED,
-      "check_coin_balance");
+      TALER_EC_EXCHANGE_GENERIC_COIN_CONFLICTING_DENOMINATION_KEY,
+      &coin->coin_pub);
     return GNUNET_DB_STATUS_HARD_ERROR;
-  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
-    /* handled below */
-    break;
-  }
-  if (! zombie_ok)
-  {
-    GNUNET_break_op (0);
-    *mhd_ret = TALER_MHD_reply_with_error (
+  case TALER_EXCHANGEDB_CKS_AGE_CONFLICT:
+    *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (
       connection,
-      MHD_HTTP_BAD_REQUEST,
-      TALER_EC_EXCHANGE_MELT_COIN_EXPIRED_NO_ZOMBIE,
-      NULL);
+      TALER_EC_EXCHANGE_GENERIC_COIN_CONFLICTING_AGE_HASH,
+      &coin->coin_pub);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
-  if (balance_ok)
-    return qs;
-  /* balance is not OK, do expensive call to compute full error message */
-  qs = check_coin_balance (connection,
-                           coin_pub,
-                           coin_value,
-                           op_cost,
-                           check_recoup,
-                           zombie_required,
-                           mhd_ret);
-  if (qs < 0)
-    return qs; /* we expected to fail (same check as before!) */
-  GNUNET_break (0); /* stored procedure and individual statements
-                       disagree, should be impossible! */
-  *mhd_ret = TALER_MHD_reply_with_error (
-    connection,
-    MHD_HTTP_INTERNAL_SERVER_ERROR,
-    TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
-    "stored procedure disagrees with full coin transaction history fetch");
+  GNUNET_assert (0);
   return GNUNET_DB_STATUS_HARD_ERROR;
 }
 
diff --git a/src/exchange/taler-exchange-httpd_db.h b/src/exchange/taler-exchange-httpd_db.h
index 5ee3b41d5..7c954ffe1 100644
--- a/src/exchange/taler-exchange-httpd_db.h
+++ b/src/exchange/taler-exchange-httpd_db.h
@@ -32,45 +32,18 @@
  *
  * @param coin the coin to make known
  * @param connection MHD request context
+ * @param[out] known_coin_id set to the unique ID for the coin in the DB
  * @param[out] mhd_ret set to MHD status on error
  * @return transaction status, negative on error (@a mhd_ret will be set in this case)
  */
 enum GNUNET_DB_QueryStatus
 TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
                      struct MHD_Connection *connection,
+                     uint64_t *known_coin_id,
                      MHD_RESULT *mhd_ret);
 
 
 /**
- * Check that a coin has an adequate balance so that we can
- * commit the current transaction. If the balance is
- * insufficient for all transactions associated with the
- * coin, return a hard error.
- *
- * We first do a "fast" check using a stored procedure, and
- * only obtain the "full" data on failure (for performance).
- *
- * @param connection HTTP connection to report hard errors on
- * @param coin_pub coin to analyze
- * @param coin_value total value of the original coin (by denomination)
- * @param op_cost cost of the current operation (for error reporting)
- * @param check_recoup should we include recoup transactions in the check
- * @param zombie_required additional requirement that the coin must
- *          be a zombie coin, or also hard failure
- * @param[out] mhd_ret set to response status code, on hard error only
- * @return transaction status
- */
-enum GNUNET_DB_QueryStatus
-TEH_check_coin_balance (struct MHD_Connection *connection,
-                        const struct TALER_CoinSpendPublicKeyP *coin_pub,
-                        const struct TALER_Amount *coin_value,
-                        const struct TALER_Amount *op_cost,
-                        bool check_recoup,
-                        bool zombie_required,
-                        MHD_RESULT *mhd_ret);
-
-
-/**
  * Function implementing a database transaction.  Runs the transaction
  * logic; IF it returns a non-error code, the transaction logic MUST
  * NOT queue a MHD response.  IF it returns an hard error, the
diff --git a/src/exchange/taler-exchange-httpd_deposit.c b/src/exchange/taler-exchange-httpd_deposit.c
index 11094d11c..84741b5c3 100644
--- a/src/exchange/taler-exchange-httpd_deposit.c
+++ b/src/exchange/taler-exchange-httpd_deposit.c
@@ -47,6 +47,7 @@
  * @param connection connection to the client
  * @param coin_pub public key of the coin
  * @param h_wire hash of wire details
+ * @param h_extensions hash of applicable extensions
  * @param h_contract_terms hash of contract details
  * @param exchange_timestamp exchange's timestamp
  * @param refund_deadline until when this deposit be refunded
@@ -118,23 +119,21 @@ struct DepositContext
 
   /**
    * Our timestamp (when we received the request).
+   * Possibly updated by the transaction if the
+   * request is idempotent (was repeated).
    */
   struct GNUNET_TIME_Timestamp exchange_timestamp;
 
   /**
-   * Calculated hash over the wire details.
+   * Hash of the payto URI.
    */
-  struct TALER_MerchantWireHash h_wire;
+  struct TALER_PaytoHash h_payto;
 
   /**
-   * Value of the coin.
+   * Row of of the coin in the known_coins table.
    */
-  struct TALER_Amount value;
+  uint64_t known_coin_id;
 
-  /**
-   * payto:// URI of the credited account.
-   */
-  const char *payto_uri;
 };
 
 
@@ -157,15 +156,18 @@ deposit_transaction (void *cls,
                      MHD_RESULT *mhd_ret)
 {
   struct DepositContext *dc = cls;
-  const struct TALER_EXCHANGEDB_Deposit *deposit = dc->deposit;
-  struct TALER_Amount spent;
   enum GNUNET_DB_QueryStatus qs;
-  struct TALER_Amount deposit_fee;
-
-  /* begin optimistically: assume this is a new deposit */
-  qs = TEH_plugin->insert_deposit (TEH_plugin->cls,
-                                   dc->exchange_timestamp,
-                                   deposit);
+  bool balance_ok;
+  bool in_conflict;
+
+  qs = TEH_plugin->do_deposit (TEH_plugin->cls,
+                               dc->deposit,
+                               dc->known_coin_id,
+                               &dc->h_payto,
+                               false, /* FIXME-OEC: extension blocked */
+                               &dc->exchange_timestamp,
+                               &balance_ok,
+                               &in_conflict);
   if (qs < 0)
   {
     if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
@@ -174,73 +176,30 @@ deposit_transaction (void *cls,
     *mhd_ret = TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_INTERNAL_SERVER_ERROR,
                                            TALER_EC_GENERIC_DB_STORE_FAILED,
-                                           NULL);
+                                           "deposit");
     return qs;
   }
-  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+  if (in_conflict)
   {
-    /* Check for idempotency: did we get this request before? */
-    qs = TEH_plugin->have_deposit (TEH_plugin->cls,
-                                   deposit,
-                                   &deposit_fee,
-                                   &dc->exchange_timestamp);
-    if (qs < 0)
-    {
-      if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-        return qs;
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                             "have_deposit");
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-    {
-      /* Conflict on insert, but record does not exist?
-         That makes no sense. */
-      GNUNET_break (0);
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-
-    {
-      struct TALER_Amount amount_without_fee;
-
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                  "/deposit replay, accepting again!\n");
-      GNUNET_assert (0 <=
-                     TALER_amount_subtract (&amount_without_fee,
-                                            &deposit->amount_with_fee,
-                                            &deposit_fee));
-      *mhd_ret = reply_deposit_success (connection,
-                                        &deposit->coin.coin_pub,
-                                        &dc->h_wire,
-                                        NULL /* h_extensions! */,
-                                        &deposit->h_contract_terms,
-                                        dc->exchange_timestamp,
-                                        deposit->refund_deadline,
-                                        deposit->wire_deadline,
-                                        &deposit->merchant_pub,
-                                        &amount_without_fee);
-      /* Note: we return "hard error" to ensure the wrapper
-         does not retry the transaction, and to also not generate
-         a "fresh" response (as we would on "success") */
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
+    TEH_plugin->rollback (TEH_plugin->cls);
+    *mhd_ret
+      = TEH_RESPONSE_reply_coin_insufficient_funds (
+          connection,
+          TALER_EC_EXCHANGE_DEPOSIT_CONFLICTING_CONTRACT,
+          &dc->deposit->coin.coin_pub);
+    return GNUNET_DB_STATUS_HARD_ERROR;
   }
-
-  /* Start with zero cost, as we already added this melt transaction
-     to the DB, so we will see it again during the queries below. */
-  GNUNET_assert (GNUNET_OK ==
-                 TALER_amount_set_zero (TEH_currency,
-                                        &spent));
-
-  return TEH_check_coin_balance (connection,
-                                 &deposit->coin.coin_pub,
-                                 &dc->value,
-                                 &deposit->amount_with_fee,
-                                 false, /* no need for recoup */
-                                 false, /* no need for zombie */
-                                 mhd_ret);
+  if (! balance_ok)
+  {
+    TEH_plugin->rollback (TEH_plugin->cls);
+    *mhd_ret
+      = TEH_RESPONSE_reply_coin_insufficient_funds (
+          connection,
+          TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS,
+          &dc->deposit->coin.coin_pub);
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  }
+  return qs;
 }
 
 
@@ -263,9 +222,10 @@ TEH_handler_deposit (struct MHD_Connection *connection,
 {
   struct DepositContext dc;
   struct TALER_EXCHANGEDB_Deposit deposit;
+  const char *payto_uri;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_string ("merchant_payto_uri",
-                             &dc.payto_uri),
+                             &payto_uri),
     GNUNET_JSON_spec_fixed_auto ("wire_salt",
                                  &deposit.wire_salt),
     TALER_JSON_spec_amount ("contribution",
@@ -290,6 +250,7 @@ TEH_handler_deposit (struct MHD_Connection *connection,
                                 &deposit.wire_deadline),
     GNUNET_JSON_spec_end ()
   };
+  struct TALER_MerchantWireHash h_wire;
 
   memset (&deposit,
           0,
@@ -316,7 +277,7 @@ TEH_handler_deposit (struct MHD_Connection *connection,
   {
     char *emsg;
 
-    emsg = TALER_payto_validate (dc.payto_uri);
+    emsg = TALER_payto_validate (payto_uri);
     if (NULL != emsg)
     {
       MHD_RESULT ret;
@@ -331,7 +292,6 @@ TEH_handler_deposit (struct MHD_Connection *connection,
       return ret;
     }
   }
-  deposit.receiver_wire_account = (char *) dc.payto_uri;
   if (GNUNET_TIME_timestamp_cmp (deposit.refund_deadline,
                                  >,
                                  deposit.wire_deadline))
@@ -343,9 +303,12 @@ TEH_handler_deposit (struct MHD_Connection *connection,
                                        TALER_EC_EXCHANGE_DEPOSIT_REFUND_DEADLINE_AFTER_WIRE_DEADLINE,
                                        NULL);
   }
-  TALER_merchant_wire_signature_hash (dc.payto_uri,
+  deposit.receiver_wire_account = (char *) payto_uri;
+  TALER_payto_hash (payto_uri,
+                    &dc.h_payto);
+  TALER_merchant_wire_signature_hash (payto_uri,
                                       &deposit.wire_salt,
-                                      &dc.h_wire);
+                                      &h_wire);
   dc.deposit = &deposit;
 
   /* new deposit */
@@ -366,42 +329,30 @@ TEH_handler_deposit (struct MHD_Connection *connection,
     if (GNUNET_TIME_absolute_is_past (dk->meta.expire_deposit.abs_time))
     {
       /* This denomination is past the expiration time for deposits */
-      struct GNUNET_TIME_Timestamp now;
-
-      now = GNUNET_TIME_timestamp_get ();
       GNUNET_JSON_parse_free (spec);
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         connection,
         &deposit.coin.denom_pub_hash,
-        now,
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
         "DEPOSIT");
     }
     if (GNUNET_TIME_absolute_is_future (dk->meta.start.abs_time))
     {
       /* This denomination is not yet valid */
-      struct GNUNET_TIME_Timestamp now;
-
-      now = GNUNET_TIME_timestamp_get ();
       GNUNET_JSON_parse_free (spec);
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         connection,
         &deposit.coin.denom_pub_hash,
-        now,
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
         "DEPOSIT");
     }
     if (dk->recoup_possible)
     {
-      struct GNUNET_TIME_Timestamp now;
-
-      now = GNUNET_TIME_timestamp_get ();
       /* This denomination has been revoked */
       GNUNET_JSON_parse_free (spec);
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         connection,
         &deposit.coin.denom_pub_hash,
-        now,
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_REVOKED,
         "DEPOSIT");
     }
@@ -419,7 +370,6 @@ TEH_handler_deposit (struct MHD_Connection *connection,
                                          TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
                                          NULL);
     }
-    dc.value = dk->meta.value;
   }
   if (0 < TALER_amount_cmp (&deposit.deposit_fee,
                             &deposit.amount_with_fee))
@@ -435,7 +385,7 @@ TEH_handler_deposit (struct MHD_Connection *connection,
   if (GNUNET_OK !=
       TALER_wallet_deposit_verify (&deposit.amount_with_fee,
                                    &deposit.deposit_fee,
-                                   &dc.h_wire,
+                                   &h_wire,
                                    &deposit.h_contract_terms,
                                    NULL /* h_extensions! */,
                                    &deposit.coin.denom_pub_hash,
@@ -470,6 +420,7 @@ TEH_handler_deposit (struct MHD_Connection *connection,
     /* make sure coin is 'known' in database */
     qs = TEH_make_coin_known (&deposit.coin,
                               connection,
+                              &dc.known_coin_id,
                               &mhd_ret);
     /* no transaction => no serialization failures should be possible */
     GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
@@ -506,7 +457,7 @@ TEH_handler_deposit (struct MHD_Connection *connection,
                                           &deposit.deposit_fee));
     res = reply_deposit_success (connection,
                                  &deposit.coin.coin_pub,
-                                 &dc.h_wire,
+                                 &h_wire,
                                  NULL /* h_extensions! */,
                                  &deposit.h_contract_terms,
                                  dc.exchange_timestamp,
diff --git a/src/exchange/taler-exchange-httpd_keys.c b/src/exchange/taler-exchange-httpd_keys.c
index a9cd864aa..5d7476771 100644
--- a/src/exchange/taler-exchange-httpd_keys.c
+++ b/src/exchange/taler-exchange-httpd_keys.c
@@ -57,7 +57,7 @@
  * #TALER_PROTOCOL_CURRENT and #TALER_PROTOCOL_AGE in
  * exchange_api_handle.c!
  */
-#define EXCHANGE_PROTOCOL_VERSION "11:0:1"
+#define EXCHANGE_PROTOCOL_VERSION "12:0:0"
 
 
 /**
diff --git a/src/exchange/taler-exchange-httpd_melt.c b/src/exchange/taler-exchange-httpd_melt.c
index e4b2af290..54f1385d7 100644
--- a/src/exchange/taler-exchange-httpd_melt.c
+++ b/src/exchange/taler-exchange-httpd_melt.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014-2020 Taler Systems SA
+  Copyright (C) 2014-2021 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Affero General Public License as published by the Free Software
@@ -90,6 +90,11 @@ struct MeltContext
   struct TALER_EXCHANGEDB_Refresh refresh_session;
 
   /**
+   * UUID of the coin in the known_coins table.
+   */
+  uint64_t known_coin_id;
+
+  /**
    * Information about the @e coin's value.
    */
   struct TALER_Amount coin_value;
@@ -141,15 +146,19 @@ melt_transaction (void *cls,
 {
   struct MeltContext *rmc = cls;
   enum GNUNET_DB_QueryStatus qs;
-  uint32_t noreveal_index;
+  bool balance_ok;
 
   /* pick challenge and persist it */
   rmc->refresh_session.noreveal_index
     = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG,
                                 TALER_CNC_KAPPA);
+
   if (0 >
-      (qs = TEH_plugin->insert_melt (TEH_plugin->cls,
-                                     &rmc->refresh_session)))
+      (qs = TEH_plugin->do_melt (TEH_plugin->cls,
+                                 &rmc->refresh_session,
+                                 rmc->known_coin_id,
+                                 &rmc->zombie_required,
+                                 &balance_ok)))
   {
     if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
     {
@@ -161,64 +170,43 @@ melt_transaction (void *cls,
     }
     return qs;
   }
-  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+  GNUNET_break (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs);
+  if (rmc->zombie_required)
   {
-    /* Check if we already created a matching refresh_session */
-    qs = TEH_plugin->get_melt_index (TEH_plugin->cls,
-                                     &rmc->refresh_session.rc,
-                                     &noreveal_index);
-    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
-    {
-      TALER_LOG_DEBUG ("Coin was previously melted, returning old reply\n");
-      *mhd_ret = reply_melt_success (connection,
-                                     &rmc->refresh_session.rc,
-                                     noreveal_index);
-      /* Note: we return "hard error" to ensure the wrapper
-         does not retry the transaction, and to also not generate
-         a "fresh" response (as we would on "success") */
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-    if (0 > qs)
-    {
-      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-        *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                               MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                               TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                               "melt index");
-      return qs;
-    }
-    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-    {
-      /* Conflict on insert, but record does not exist?
-         That makes no sense. */
-      GNUNET_break (0);
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
+    GNUNET_break_op (0);
+    TEH_plugin->rollback (TEH_plugin->cls);
+    *mhd_ret = TALER_MHD_reply_with_error (connection,
+                                           MHD_HTTP_BAD_REQUEST,
+                                           TALER_EC_EXCHANGE_MELT_COIN_EXPIRED_NO_ZOMBIE,
+                                           NULL);
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  }
+  if (! balance_ok)
+  {
+    TEH_plugin->rollback (TEH_plugin->cls);
+    *mhd_ret
+      = TEH_RESPONSE_reply_coin_insufficient_funds (
+          connection,
+          TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS,
+          &rmc->refresh_session.coin.coin_pub);
+    return GNUNET_DB_STATUS_HARD_ERROR;
   }
-  return TEH_check_coin_balance (connection,
-                                 &rmc->refresh_session.coin.coin_pub,
-                                 &rmc->coin_value,
-                                 &rmc->refresh_session.amount_with_fee,
-                                 true,
-                                 rmc->zombie_required,
-                                 mhd_ret);
+  /* All good, commit, final response will be generated by caller */
+  return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
 }
 
 
 /**
  * Handle a "melt" request after the first parsing has
- * happened.  We now need to validate the coins being melted and the
- * session signature and then hand things of to execute the melt
- * operation.  This function parses the JSON arrays and then passes
- * processing on to #melt_transaction().
+ * happened.  Performs the database transactions.
  *
  * @param connection the MHD connection to handle
  * @param[in,out] rmc details about the melt request
  * @return MHD result code
  */
 static MHD_RESULT
-handle_melt (struct MHD_Connection *connection,
-             struct MeltContext *rmc)
+database_melt (struct MHD_Connection *connection,
+               struct MeltContext *rmc)
 {
   if (GNUNET_SYSERR ==
       TEH_plugin->preflight (TEH_plugin->cls))
@@ -230,36 +218,6 @@ handle_melt (struct MHD_Connection *connection,
                                        "preflight failure");
   }
 
-  /* verify signature of coin for melt operation */
-  {
-    struct TALER_RefreshMeltCoinAffirmationPS body = {
-      .purpose.size = htonl (sizeof (body)),
-      .purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_MELT),
-      .rc = rmc->refresh_session.rc,
-      .h_denom_pub = rmc->refresh_session.coin.denom_pub_hash,
-      .coin_pub = rmc->refresh_session.coin.coin_pub
-    };
-
-    TALER_amount_hton (&body.amount_with_fee,
-                       &rmc->refresh_session.amount_with_fee);
-    TALER_amount_hton (&body.melt_fee,
-                       &rmc->coin_refresh_fee);
-
-    if (GNUNET_OK !=
-        GNUNET_CRYPTO_eddsa_verify (
-          TALER_SIGNATURE_WALLET_COIN_MELT,
-          &body,
-          &rmc->refresh_session.coin_sig.eddsa_signature,
-          &rmc->refresh_session.coin.coin_pub.eddsa_pub))
-    {
-      GNUNET_break_op (0);
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_FORBIDDEN,
-                                         TALER_EC_EXCHANGE_MELT_COIN_SIGNATURE_INVALID,
-                                         NULL);
-    }
-  }
-
   /* first, make sure coin is known */
   if (! rmc->coin_is_dirty)
   {
@@ -268,6 +226,7 @@ handle_melt (struct MHD_Connection *connection,
 
     qs = TEH_make_coin_known (&rmc->refresh_session.coin,
                               connection,
+                              &rmc->known_coin_id,
                               &mhd_ret);
     /* no transaction => no serialization failures should be possible */
     GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
@@ -305,8 +264,8 @@ handle_melt (struct MHD_Connection *connection,
  * @return MHD status code
  */
 static MHD_RESULT
-check_for_denomination_key (struct MHD_Connection *connection,
-                            struct MeltContext *rmc)
+check_melt_valid (struct MHD_Connection *connection,
+                  struct MeltContext *rmc)
 {
   /* Baseline: check if deposits/refreshs are generally
      simply still allowed for this denomination */
@@ -321,30 +280,64 @@ check_for_denomination_key (struct MHD_Connection *connection,
     return mret;
   if (GNUNET_TIME_absolute_is_past (dk->meta.expire_legal.abs_time))
   {
-    struct GNUNET_TIME_Timestamp now;
-
-    now = GNUNET_TIME_timestamp_get ();
     /* Way too late now, even zombies have expired */
     return TEH_RESPONSE_reply_expired_denom_pub_hash (
       connection,
       &rmc->refresh_session.coin.denom_pub_hash,
-      now,
       TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
       "MELT");
   }
   if (GNUNET_TIME_absolute_is_future (dk->meta.start.abs_time))
   {
-    struct GNUNET_TIME_Timestamp now;
-
-    now = GNUNET_TIME_timestamp_get ();
     /* This denomination is not yet valid */
     return TEH_RESPONSE_reply_expired_denom_pub_hash (
       connection,
       &rmc->refresh_session.coin.denom_pub_hash,
-      now,
       TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
       "MELT");
   }
+
+  rmc->coin_refresh_fee = dk->meta.fee_refresh;
+  rmc->coin_value = dk->meta.value;
+  /* sanity-check that "total melt amount > melt fee" */
+  if (0 <
+      TALER_amount_cmp (&rmc->coin_refresh_fee,
+                        &rmc->refresh_session.amount_with_fee))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_BAD_REQUEST,
+                                       TALER_EC_EXCHANGE_MELT_FEES_EXCEED_CONTRIBUTION,
+                                       NULL);
+  }
+
+  if (GNUNET_OK !=
+      TALER_test_coin_valid (&rmc->refresh_session.coin,
+                             &dk->denom_pub))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_FORBIDDEN,
+                                       TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
+                                       NULL);
+  }
+
+  /* verify signature of coin for melt operation */
+  if (GNUNET_OK !=
+      TALER_wallet_melt_verify (&rmc->refresh_session.amount_with_fee,
+                                &rmc->coin_refresh_fee,
+                                &rmc->refresh_session.rc,
+                                &rmc->refresh_session.coin.denom_pub_hash,
+                                &rmc->refresh_session.coin.coin_pub,
+                                &rmc->refresh_session.coin_sig))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_FORBIDDEN,
+                                       TALER_EC_EXCHANGE_MELT_COIN_SIGNATURE_INVALID,
+                                       NULL);
+  }
+
   if (GNUNET_TIME_absolute_is_past (dk->meta.expire_deposit.abs_time))
   {
     /* We are past deposit expiration time, but maybe this is a zombie? */
@@ -357,6 +350,7 @@ check_for_denomination_key (struct MHD_Connection *connection,
     qs = TEH_plugin->get_coin_denomination (
       TEH_plugin->cls,
       &rmc->refresh_session.coin.coin_pub,
+      &rmc->known_coin_id,
       &denom_hash);
     if (0 > qs)
     {
@@ -369,14 +363,10 @@ check_for_denomination_key (struct MHD_Connection *connection,
     }
     if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
     {
-      struct GNUNET_TIME_Timestamp now;
-
-      now = GNUNET_TIME_timestamp_get ();
       /* We never saw this coin before, so _this_ justification is not OK */
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         connection,
         &rmc->refresh_session.coin.denom_pub_hash,
-        now,
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
         "MELT");
     }
@@ -389,67 +379,25 @@ check_for_denomination_key (struct MHD_Connection *connection,
                        &rmc->refresh_session.coin.denom_pub_hash))
     {
       GNUNET_break_op (0);
-      // => this is probably the wrong call, as this
-      // is NOT about insufficient funds!
-      // (see also taler-exchange-httpd_db.c for an equivalent issue)
-      return TEH_RESPONSE_reply_coin_insufficient_funds (
+      return TALER_MHD_reply_with_ec (
         connection,
         TALER_EC_EXCHANGE_GENERIC_COIN_CONFLICTING_DENOMINATION_KEY,
-        &rmc->refresh_session.coin.coin_pub,
-        NULL);
+        TALER_B2S (&denom_hash));
     }
     rmc->zombie_required = true;   /* check later that zombie is satisfied */
   }
 
-  rmc->coin_refresh_fee = dk->meta.fee_refresh;
-  rmc->coin_value = dk->meta.value;
-  /* check coin is actually properly signed */
-  if (GNUNET_OK !=
-      TALER_test_coin_valid (&rmc->refresh_session.coin,
-                             &dk->denom_pub))
-  {
-    GNUNET_break_op (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_FORBIDDEN,
-                                       TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
-                                       NULL);
-  }
-
-  /* sanity-check that "total melt amount > melt fee" */
-  if (0 <
-      TALER_amount_cmp (&rmc->coin_refresh_fee,
-                        &rmc->refresh_session.amount_with_fee))
-  {
-    GNUNET_break_op (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_EXCHANGE_MELT_FEES_EXCEED_CONTRIBUTION,
-                                       NULL);
-  }
-  return handle_melt (connection,
-                      rmc);
+  return database_melt (connection,
+                        rmc);
 }
 
 
-/**
- * Handle a "/coins/$COIN_PUB/melt" request.  Parses the request into the JSON
- * components and then hands things of to #check_for_denomination_key() to
- * validate the melted coins, the signature and execute the melt using
- * handle_melt().
-
- * @param connection the MHD connection to handle
- * @param coin_pub public key of the coin
- * @param root uploaded JSON data
- * @return MHD result code
- */
 MHD_RESULT
 TEH_handler_melt (struct MHD_Connection *connection,
                   const struct TALER_CoinSpendPublicKeyP *coin_pub,
                   const json_t *root)
 {
   struct MeltContext rmc;
-  enum GNUNET_GenericReturnValue ret;
-  MHD_RESULT res;
   struct GNUNET_JSON_Specification spec[] = {
     TALER_JSON_spec_denom_sig ("denom_sig",
                                &rmc.refresh_session.coin.denom_sig),
@@ -469,16 +417,24 @@ TEH_handler_melt (struct MHD_Connection *connection,
           0,
           sizeof (rmc));
   rmc.refresh_session.coin.coin_pub = *coin_pub;
-  ret = TALER_MHD_parse_json_data (connection,
-                                   root,
-                                   spec);
-  if (GNUNET_OK != ret)
-    return (GNUNET_SYSERR == ret) ? MHD_NO : MHD_YES;
-
-  res = check_for_denomination_key (connection,
-                                    &rmc);
-  GNUNET_JSON_parse_free (spec);
-  return res;
+
+  {
+    enum GNUNET_GenericReturnValue ret;
+    ret = TALER_MHD_parse_json_data (connection,
+                                     root,
+                                     spec);
+    if (GNUNET_OK != ret)
+      return (GNUNET_SYSERR == ret) ? MHD_NO : MHD_YES;
+  }
+
+  {
+    MHD_RESULT res;
+
+    res = check_melt_valid (connection,
+                            &rmc);
+    GNUNET_JSON_parse_free (spec);
+    return res;
+  }
 }
 
 
diff --git a/src/exchange/taler-exchange-httpd_metrics.c b/src/exchange/taler-exchange-httpd_metrics.c
index 2ea889ff0..8c8cd343a 100644
--- a/src/exchange/taler-exchange-httpd_metrics.c
+++ b/src/exchange/taler-exchange-httpd_metrics.c
@@ -51,18 +51,12 @@ TEH_handler_metrics (struct TEH_RequestContext *rc,
                    "taler_exchange_serialization_failures{type=\"%s\"} %llu\n"
                    "taler_exchange_serialization_failures{type=\"%s\"} %llu\n"
                    "taler_exchange_serialization_failures{type=\"%s\"} %llu\n"
-                   "taler_exchange_serialization_failures{type=\"%s\"} %llu\n"
-                   "taler_exchange_serialization_failures{type=\"%s\"} %llu\n"
-                   "taler_exchange_serialization_failures{type=\"%s\"} %llu\n"
                    "# HELP taler_exchange_received_requests "
                    " number of received requests by type\n"
                    "# TYPE taler_exchange_received_requests counter\n"
                    "taler_exchange_received_requests{type=\"%s\"} %llu\n"
                    "taler_exchange_received_requests{type=\"%s\"} %llu\n"
                    "taler_exchange_received_requests{type=\"%s\"} %llu\n"
-                   "taler_exchange_received_requests{type=\"%s\"} %llu\n"
-                   "taler_exchange_received_requests{type=\"%s\"} %llu\n"
-                   "taler_exchange_received_requests{type=\"%s\"} %llu\n"
                    "taler_exchange_received_requests{type=\"%s\"} %llu\n",
                    "other",
                    TEH_METRICS_num_conflict[TEH_MT_OTHER],
@@ -72,12 +66,6 @@ TEH_handler_metrics (struct TEH_RequestContext *rc,
                    TEH_METRICS_num_conflict[TEH_MT_WITHDRAW],
                    "melt",
                    TEH_METRICS_num_conflict[TEH_MT_MELT],
-                   "reveal-precheck",
-                   TEH_METRICS_num_conflict[TEH_MT_REVEAL_PRECHECK],
-                   "reveal",
-                   TEH_METRICS_num_conflict[TEH_MT_REVEAL],
-                   "reveal-persist",
-                   TEH_METRICS_num_conflict[TEH_MT_REVEAL_PERSIST],
                    "other",
                    TEH_METRICS_num_requests[TEH_MT_OTHER],
                    "deposit",
@@ -85,13 +73,7 @@ TEH_handler_metrics (struct TEH_RequestContext *rc,
                    "withdraw",
                    TEH_METRICS_num_requests[TEH_MT_WITHDRAW],
                    "melt",
-                   TEH_METRICS_num_requests[TEH_MT_MELT],
-                   "reveal-precheck",
-                   TEH_METRICS_num_requests[TEH_MT_REVEAL_PRECHECK],
-                   "reveal",
-                   TEH_METRICS_num_requests[TEH_MT_REVEAL],
-                   "reveal-persist",
-                   TEH_METRICS_num_requests[TEH_MT_REVEAL_PERSIST]);
+                   TEH_METRICS_num_requests[TEH_MT_MELT]);
   resp = MHD_create_response_from_buffer (strlen (reply),
                                           reply,
                                           MHD_RESPMEM_MUST_FREE);
diff --git a/src/exchange/taler-exchange-httpd_metrics.h b/src/exchange/taler-exchange-httpd_metrics.h
index 39e463169..55e5372a7 100644
--- a/src/exchange/taler-exchange-httpd_metrics.h
+++ b/src/exchange/taler-exchange-httpd_metrics.h
@@ -35,10 +35,7 @@ enum TEH_MetricType
   TEH_MT_DEPOSIT = 1,
   TEH_MT_WITHDRAW = 2,
   TEH_MT_MELT = 3,
-  TEH_MT_REVEAL_PRECHECK = 4,
-  TEH_MT_REVEAL = 5,
-  TEH_MT_REVEAL_PERSIST = 6,
-  TEH_MT_COUNT = 7 /* MUST BE LAST! */
+  TEH_MT_COUNT = 4 /* MUST BE LAST! */
 };
 
 
diff --git a/src/exchange/taler-exchange-httpd_recoup-refresh.c b/src/exchange/taler-exchange-httpd_recoup-refresh.c
new file mode 100644
index 000000000..acadc999e
--- /dev/null
+++ b/src/exchange/taler-exchange-httpd_recoup-refresh.c
@@ -0,0 +1,411 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2017-2021 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
+
+  You should have received a copy of the GNU Affero General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-exchange-httpd_recoup-refresh.c
+ * @brief Handle /recoup-refresh requests; parses the POST and JSON and
+ *        verifies the coin signature before handing things off
+ *        to the database.
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <gnunet/gnunet_util_lib.h>
+#include <gnunet/gnunet_json_lib.h>
+#include <jansson.h>
+#include <microhttpd.h>
+#include <pthread.h>
+#include "taler_json_lib.h"
+#include "taler_mhd_lib.h"
+#include "taler-exchange-httpd_db.h"
+#include "taler-exchange-httpd_recoup-refresh.h"
+#include "taler-exchange-httpd_responses.h"
+#include "taler-exchange-httpd_keys.h"
+#include "taler_exchangedb_lib.h"
+
+
+/**
+ * Closure for #recoup_refresh_transaction().
+ */
+struct RecoupContext
+{
+
+  /**
+   * Set by #recoup_transaction() to the old coin that will
+   * receive the recoup.
+   */
+  struct TALER_CoinSpendPublicKeyP old_coin_pub;
+
+  /**
+   * Details about the coin.
+   */
+  const struct TALER_CoinPublicInfo *coin;
+
+  /**
+   * Key used to blind the coin.
+   */
+  const union TALER_DenominationBlindingKeyP *coin_bks;
+
+  /**
+   * Signature of the coin requesting recoup.
+   */
+  const struct TALER_CoinSpendSignatureP *coin_sig;
+
+  /**
+   * The amount requested to be recouped.
+   */
+  const struct TALER_Amount *requested_amount;
+
+  /**
+   * Unique ID of the coin in the known_coins table.
+   */
+  uint64_t known_coin_id;
+
+  /**
+   * Unique ID of the refresh reveal context of the melt for the new coin.
+   */
+  uint64_t rrc_serial;
+
+  /**
+   * Set by #recoup_transaction to the timestamp when the recoup
+   * was accepted.
+   */
+  struct GNUNET_TIME_Timestamp now;
+
+};
+
+
+/**
+ * Execute a "recoup-refresh".  The validity of the coin and signature have
+ * already been checked.  The database must now check that the coin is not
+ * (double) spent, and execute the transaction.
+ *
+ * IF it returns a non-error code, the transaction logic MUST
+ * NOT queue a MHD response.  IF it returns an hard error, the
+ * transaction logic MUST queue a MHD response and set @a mhd_ret.  IF
+ * it returns the soft error code, the function MAY be called again to
+ * retry and MUST not queue a MHD response.
+ *
+ * @param cls the `struct RecoupContext *`
+ * @param connection MHD request which triggered the transaction
+ * @param[out] mhd_ret set to MHD response status for @a connection,
+ *             if transaction failed (!)
+ * @return transaction status code
+ */
+static enum GNUNET_DB_QueryStatus
+recoup_refresh_transaction (void *cls,
+                            struct MHD_Connection *connection,
+                            MHD_RESULT *mhd_ret)
+{
+  struct RecoupContext *pc = cls;
+  enum GNUNET_DB_QueryStatus qs;
+  bool recoup_ok;
+  bool internal_failure;
+
+  /* Finally, store new refund data */
+  pc->now = GNUNET_TIME_timestamp_get ();
+  qs = TEH_plugin->do_recoup_refresh (TEH_plugin->cls,
+                                      &pc->old_coin_pub,
+                                      pc->rrc_serial,
+                                      pc->requested_amount,
+                                      pc->coin_bks,
+                                      &pc->coin->coin_pub,
+                                      pc->known_coin_id,
+                                      pc->coin_sig,
+                                      &pc->now,
+                                      &recoup_ok,
+                                      &internal_failure);
+  if (0 > qs)
+  {
+    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
+      *mhd_ret = TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_INTERNAL_SERVER_ERROR,
+        TALER_EC_GENERIC_DB_FETCH_FAILED,
+        "do_recoup_refresh");
+    return qs;
+  }
+
+  if (internal_failure)
+  {
+    GNUNET_break (0);
+    *mhd_ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
+      "coin transaction history");
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  }
+  if (! recoup_ok)
+  {
+    *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (
+      connection,
+      TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS,
+      &pc->coin->coin_pub);
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  }
+  return qs;
+}
+
+
+/**
+ * We have parsed the JSON information about the recoup request. Do
+ * some basic sanity checks (especially that the signature on the
+ * request and coin is valid) and then execute the recoup operation.
+ * Note that we need the DB to check the fee structure, so this is not
+ * done here but during the recoup_transaction().
+ *
+ * @param connection the MHD connection to handle
+ * @param coin information about the coin
+ * @param coin_bks blinding data of the coin (to be checked)
+ * @param coin_sig signature of the coin
+ * @param requested_amount requested amount to be recouped
+ * @return MHD result code
+ */
+static MHD_RESULT
+verify_and_execute_recoup_refresh (
+  struct MHD_Connection *connection,
+  const struct TALER_CoinPublicInfo *coin,
+  const union TALER_DenominationBlindingKeyP *coin_bks,
+  const struct TALER_CoinSpendSignatureP *coin_sig,
+  const struct TALER_Amount *requested_amount)
+{
+  struct RecoupContext pc;
+  const struct TEH_DenominationKey *dk;
+  MHD_RESULT mret;
+  struct TALER_BlindedCoinHash h_blind;
+
+  /* check denomination exists and is in recoup mode */
+  dk = TEH_keys_denomination_by_hash (&coin->denom_pub_hash,
+                                      connection,
+                                      &mret);
+  if (NULL == dk)
+    return mret;
+  if (GNUNET_TIME_absolute_is_past (dk->meta.expire_deposit.abs_time))
+  {
+    /* This denomination is past the expiration time for recoup */
+    return TEH_RESPONSE_reply_expired_denom_pub_hash (
+      connection,
+      &coin->denom_pub_hash,
+      TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
+      "RECOUP-REFRESH");
+  }
+  if (GNUNET_TIME_absolute_is_future (dk->meta.start.abs_time))
+  {
+    /* This denomination is not yet valid */
+    return TEH_RESPONSE_reply_expired_denom_pub_hash (
+      connection,
+      &coin->denom_pub_hash,
+      TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
+      "RECOUP-REFRESH");
+  }
+  if (! dk->recoup_possible)
+  {
+    /* This denomination is not eligible for recoup */
+    return TEH_RESPONSE_reply_expired_denom_pub_hash (
+      connection,
+      &coin->denom_pub_hash,
+      TALER_EC_EXCHANGE_RECOUP_REFRESH_NOT_ELIGIBLE,
+      "RECOUP-REFRESH");
+  }
+
+  /* check denomination signature */
+  if (GNUNET_YES !=
+      TALER_test_coin_valid (coin,
+                             &dk->denom_pub))
+  {
+    TALER_LOG_WARNING ("Invalid coin passed for recoup\n");
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_FORBIDDEN,
+      TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
+      NULL);
+  }
+
+  /* check recoup request signature */
+  if (GNUNET_OK !=
+      TALER_wallet_recoup_refresh_verify (&coin->denom_pub_hash,
+                                          coin_bks,
+                                          requested_amount,
+                                          &coin->coin_pub,
+                                          coin_sig))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_FORBIDDEN,
+      TALER_EC_EXCHANGE_RECOUP_REFRESH_SIGNATURE_INVALID,
+      NULL);
+  }
+
+  {
+    void *coin_ev;
+    size_t coin_ev_size;
+    struct TALER_CoinPubHash c_hash;
+
+    if (GNUNET_OK !=
+        TALER_denom_blind (&dk->denom_pub,
+                           coin_bks,
+                           NULL, /* FIXME-Oec: TALER_AgeHash * */
+                           &coin->coin_pub,
+                           &c_hash,
+                           &coin_ev,
+                           &coin_ev_size))
+    {
+      GNUNET_break (0);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_INTERNAL_SERVER_ERROR,
+        TALER_EC_EXCHANGE_RECOUP_REFRESH_BLINDING_FAILED,
+        NULL);
+    }
+    TALER_coin_ev_hash (coin_ev,
+                        coin_ev_size,
+                        &h_blind);
+    GNUNET_free (coin_ev);
+  }
+
+  pc.coin_sig = coin_sig;
+  pc.coin_bks = coin_bks;
+  pc.coin = coin;
+  pc.requested_amount = requested_amount;
+
+  {
+    MHD_RESULT mhd_ret = MHD_NO;
+    enum GNUNET_DB_QueryStatus qs;
+
+    /* make sure coin is 'known' in database */
+    qs = TEH_make_coin_known (coin,
+                              connection,
+                              &pc.known_coin_id,
+                              &mhd_ret);
+    /* no transaction => no serialization failures should be possible */
+    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
+    if (qs < 0)
+      return mhd_ret;
+  }
+
+  {
+    enum GNUNET_DB_QueryStatus qs;
+
+    qs = TEH_plugin->get_old_coin_by_h_blind (TEH_plugin->cls,
+                                              &h_blind,
+                                              &pc.old_coin_pub,
+                                              &pc.rrc_serial);
+    if (0 > qs)
+    {
+      GNUNET_break (0);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_INTERNAL_SERVER_ERROR,
+        TALER_EC_GENERIC_DB_FETCH_FAILED,
+        "get_old_coin_by_h_blind");
+    }
+    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                  "Recoup-refresh requested for unknown envelope %s\n",
+                  GNUNET_h2s (&h_blind.hash));
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_NOT_FOUND,
+        TALER_EC_EXCHANGE_RECOUP_REFRESH_MELT_NOT_FOUND,
+        NULL);
+    }
+  }
+
+  /* Perform actual recoup transaction */
+  {
+    MHD_RESULT mhd_ret;
+
+    if (GNUNET_OK !=
+        TEH_DB_run_transaction (connection,
+                                "run recoup-refresh",
+                                TEH_MT_OTHER,
+                                &mhd_ret,
+                                &recoup_refresh_transaction,
+                                &pc))
+      return mhd_ret;
+  }
+  /* Recoup succeeded, return result */
+  return TALER_MHD_REPLY_JSON_PACK (connection,
+                                    MHD_HTTP_OK,
+                                    GNUNET_JSON_pack_data_auto (
+                                      "old_coin_pub",
+                                      &pc.old_coin_pub));
+}
+
+
+/**
+ * Handle a "/coins/$COIN_PUB/recoup-refresh" request.  Parses the JSON, and, if
+ * successful, passes the JSON data to #verify_and_execute_recoup_refresh() to further
+ * check the details of the operation specified.  If everything checks out,
+ * this will ultimately lead to the refund being executed, or rejected.
+ *
+ * @param connection the MHD connection to handle
+ * @param coin_pub public key of the coin
+ * @param root uploaded JSON data
+ * @return MHD result code
+  */
+MHD_RESULT
+TEH_handler_recoup_refresh (struct MHD_Connection *connection,
+                            const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                            const json_t *root)
+{
+  enum GNUNET_GenericReturnValue ret;
+  struct TALER_CoinPublicInfo coin;
+  union TALER_DenominationBlindingKeyP coin_bks;
+  struct TALER_CoinSpendSignatureP coin_sig;
+  struct TALER_Amount amount;
+  struct GNUNET_JSON_Specification spec[] = {
+    GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
+                                 &coin.denom_pub_hash),
+    TALER_JSON_spec_denom_sig ("denom_sig",
+                               &coin.denom_sig),
+    GNUNET_JSON_spec_fixed_auto ("coin_blind_key_secret",
+                                 &coin_bks),
+    GNUNET_JSON_spec_fixed_auto ("coin_sig",
+                                 &coin_sig),
+    TALER_JSON_spec_amount ("amount",
+                            TEH_currency,
+                            &amount),
+    GNUNET_JSON_spec_end ()
+  };
+
+  memset (&coin,
+          0,
+          sizeof (coin));
+  coin.coin_pub = *coin_pub;
+  ret = TALER_MHD_parse_json_data (connection,
+                                   root,
+                                   spec);
+  if (GNUNET_SYSERR == ret)
+    return MHD_NO; /* hard failure */
+  if (GNUNET_NO == ret)
+    return MHD_YES; /* failure */
+  {
+    MHD_RESULT res;
+
+    res = verify_and_execute_recoup_refresh (connection,
+                                             &coin,
+                                             &coin_bks,
+                                             &coin_sig,
+                                             &amount);
+    GNUNET_JSON_parse_free (spec);
+    return res;
+  }
+}
+
+
+/* end of taler-exchange-httpd_recoup-refresh.c */
diff --git a/src/exchange/taler-exchange-httpd_recoup-refresh.h b/src/exchange/taler-exchange-httpd_recoup-refresh.h
new file mode 100644
index 000000000..25c12fac3
--- /dev/null
+++ b/src/exchange/taler-exchange-httpd_recoup-refresh.h
@@ -0,0 +1,46 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2017, 2021 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
+
+  You should have received a copy of the GNU Affero General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-exchange-httpd_recoup_refresh.h
+ * @brief Handle /recoup-refresh requests
+ * @author Christian Grothoff
+ */
+#ifndef TALER_EXCHANGE_HTTPD_RECOUP_REFRESH_H
+#define TALER_EXCHANGE_HTTPD_RECOUP_REFRESH_H
+
+#include <gnunet/gnunet_util_lib.h>
+#include <microhttpd.h>
+#include "taler-exchange-httpd.h"
+
+
+/**
+ * Handle a "/coins/$COIN_PUB/recoup-refresh" request.  Parses the JSON, and, if
+ * successful, passes the JSON data to #verify_and_execute_recoup_refresh() to further
+ * check the details of the operation specified.  If everything checks out,
+ * this will ultimately lead to the refund being executed, or rejected.
+ *
+ * @param connection the MHD connection to handle
+ * @param coin_pub public key of the coin
+ * @param root uploaded JSON data
+ * @return MHD result code
+  */
+MHD_RESULT
+TEH_handler_recoup_refresh (struct MHD_Connection *connection,
+                            const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                            const json_t *root);
+
+
+#endif
diff --git a/src/exchange/taler-exchange-httpd_recoup.c b/src/exchange/taler-exchange-httpd_recoup.c
index 58495e530..28e81f9ec 100644
--- a/src/exchange/taler-exchange-httpd_recoup.c
+++ b/src/exchange/taler-exchange-httpd_recoup.c
@@ -45,9 +45,10 @@ struct RecoupContext
   struct TALER_BlindedCoinHash h_blind;
 
   /**
-   * Full value of the coin.
+   * Set by #recoup_transaction() to the reserve that will
+   * receive the recoup, if #refreshed is #GNUNET_NO.
    */
-  struct TALER_Amount value;
+  struct TALER_ReservePublicKeyP reserve_pub;
 
   /**
    * Details about the coin.
@@ -65,45 +66,29 @@ struct RecoupContext
   const struct TALER_CoinSpendSignatureP *coin_sig;
 
   /**
-   * Where does the value of the recouped coin go? Which member
-   * of the union is valid depends on @e refreshed.
+   * The amount requested to be recouped.
    */
-  union
-  {
-    /**
-     * Set by #recoup_transaction() to the reserve that will
-     * receive the recoup, if #refreshed is #GNUNET_NO.
-     */
-    struct TALER_ReservePublicKeyP reserve_pub;
-
-    /**
-     * Set by #recoup_transaction() to the old coin that will
-     * receive the recoup, if #refreshed is #GNUNET_YES.
-     */
-    struct TALER_CoinSpendPublicKeyP old_coin_pub;
-  } target;
+  const struct TALER_Amount *requested_amount;
 
   /**
-   * Set by #recoup_transaction() to the amount that will be paid back
+   * Unique ID of the withdraw operation in the reserves_out table.
    */
-  struct TALER_Amount amount;
-  const struct TALER_Amount *requested_amount;
+  uint64_t reserve_out_serial_id;
 
   /**
-   * Set by #recoup_transaction to the timestamp when the recoup
-   * was accepted.
+   * Unique ID of the coin in the known_coins table.
    */
-  struct GNUNET_TIME_Timestamp now;
+  uint64_t known_coin_id;
 
   /**
-   * true if the client claims the coin originated from a refresh.
+   * Set by #recoup_transaction to the timestamp when the recoup
+   * was accepted.
    */
-  bool refreshed;
+  struct GNUNET_TIME_Timestamp now;
 
 };
 
 
-// FIXME: this code should be simplified by using TEH_check_coin_balance()
 /**
  * Execute a "recoup".  The validity of the coin and signature have
  * already been checked.  The database must now check that the coin is
@@ -127,159 +112,53 @@ recoup_transaction (void *cls,
                     MHD_RESULT *mhd_ret)
 {
   struct RecoupContext *pc = cls;
-  struct TALER_EXCHANGEDB_TransactionList *tl;
-  struct TALER_Amount spent;
-  struct TALER_Amount recouped;
   enum GNUNET_DB_QueryStatus qs;
-  bool existing_recoup_found;
+  bool recoup_ok;
+  bool internal_failure;
 
-  /* Check whether a recoup is allowed, and if so, to which
-     reserve / account the money should go */
-
-  /* Calculate remaining balance, including recoups already applied. */
-  qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                          &pc->coin->coin_pub,
-                                          GNUNET_YES,
-                                          &tl);
+  /* Finally, store new refund data */
+  pc->now = GNUNET_TIME_timestamp_get ();
+  qs = TEH_plugin->do_recoup (TEH_plugin->cls,
+                              &pc->reserve_pub,
+                              pc->reserve_out_serial_id,
+                              pc->requested_amount,
+                              pc->coin_bks,
+                              &pc->coin->coin_pub,
+                              pc->known_coin_id,
+                              pc->coin_sig,
+                              &pc->now,
+                              &recoup_ok,
+                              &internal_failure);
   if (0 > qs)
   {
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-    {
-      GNUNET_break (0);
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                             "coin transaction list");
-    }
+      *mhd_ret = TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_INTERNAL_SERVER_ERROR,
+        TALER_EC_GENERIC_DB_FETCH_FAILED,
+        "do_recoup");
     return qs;
   }
 
-  GNUNET_assert (GNUNET_OK ==
-                 TALER_amount_set_zero (pc->value.currency,
-                                        &spent));
-  GNUNET_assert (GNUNET_OK ==
-                 TALER_amount_set_zero (pc->value.currency,
-                                        &recouped));
-  /* Check if this coin has been recouped already at least once */
-  existing_recoup_found = false;
-  for (struct TALER_EXCHANGEDB_TransactionList *pos = tl;
-       NULL != pos;
-       pos = pos->next)
-  {
-    if ( (TALER_EXCHANGEDB_TT_RECOUP == pos->type) ||
-         (TALER_EXCHANGEDB_TT_RECOUP_REFRESH == pos->type) )
-    {
-      existing_recoup_found = true;
-      break;
-    }
-  }
-  if (GNUNET_OK !=
-      TALER_EXCHANGEDB_calculate_transaction_list_totals (tl,
-                                                          &spent,
-                                                          &spent))
+  if (internal_failure)
   {
     GNUNET_break (0);
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tl);
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
-                                           "coin transaction history");
-    return GNUNET_DB_STATUS_HARD_ERROR;
-  }
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Recoup: calculated spent %s\n",
-              TALER_amount2s (&spent));
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Recoup: coin value %s\n",
-              TALER_amount2s (&pc->value));
-  if (0 >
-      TALER_amount_subtract (&pc->amount,
-                             &pc->value,
-                             &spent))
-  {
-    GNUNET_break (0);
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tl);
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_EXCHANGE_RECOUP_COIN_BALANCE_NEGATIVE,
-                                           NULL);
+    *mhd_ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
+      "do_recoup");
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
-  if (TALER_amount_is_zero (&pc->amount))
+  if (! recoup_ok)
   {
-    /* Recoup has no effect: coin fully spent! */
-    enum GNUNET_DB_QueryStatus ret;
-
-    TEH_plugin->rollback (TEH_plugin->cls);
-    if (GNUNET_NO == existing_recoup_found)
-    {
-      /* Refuse: insufficient funds for recoup */
-      *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (connection,
-                                                             TALER_EC_EXCHANGE_RECOUP_COIN_BALANCE_ZERO,
-                                                             &pc->coin->coin_pub,
-                                                             tl);
-      ret = GNUNET_DB_STATUS_HARD_ERROR;
-    }
-    else
-    {
-      /* We didn't add any new recoup transaction, but there was at least
-         one recoup before, so we give a success response (idempotency!) */
-      ret = GNUNET_DB_STATUS_SUCCESS_NO_RESULTS;
-    }
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tl);
-    return ret;
-  }
-  TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                          tl);
-  pc->now = GNUNET_TIME_timestamp_get ();
-  if (0 != TALER_amount_cmp (&pc->amount,
-                             pc->requested_amount))
-  {
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_CONFLICT,
-                                           TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS,
-                                           TALER_amount2s (&pc->amount));
+    *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (
+      connection,
+      TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS,
+      &pc->coin->coin_pub);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
-
-  /* add coin to list of wire transfers for recoup */
-  if (pc->refreshed)
-  {
-    qs = TEH_plugin->insert_recoup_refresh_request (TEH_plugin->cls,
-                                                    pc->coin,
-                                                    pc->coin_sig,
-                                                    pc->coin_bks,
-                                                    &pc->amount,
-                                                    &pc->h_blind,
-                                                    pc->now);
-  }
-  else
-  {
-    qs = TEH_plugin->insert_recoup_request (TEH_plugin->cls,
-                                            &pc->target.reserve_pub,
-                                            pc->coin,
-                                            pc->coin_sig,
-                                            pc->coin_bks,
-                                            &pc->amount,
-                                            &pc->h_blind,
-                                            pc->now);
-  }
-  if (0 > qs)
-  {
-    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-    {
-      TALER_LOG_WARNING ("Failed to store recoup information in database\n");
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_STORE_FAILED,
-                                             "recoup request");
-    }
-    return qs;
-  }
-  return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
+  return qs;
 }
 
 
@@ -295,7 +174,6 @@ recoup_transaction (void *cls,
  * @param coin_bks blinding data of the coin (to be checked)
  * @param coin_sig signature of the coin
  * @param requested_amount requested amount to be recouped
- * @param refreshed true if the coin was refreshed
  * @return MHD result code
  */
 static MHD_RESULT
@@ -304,12 +182,10 @@ verify_and_execute_recoup (
   const struct TALER_CoinPublicInfo *coin,
   const union TALER_DenominationBlindingKeyP *coin_bks,
   const struct TALER_CoinSpendSignatureP *coin_sig,
-  const struct TALER_Amount *requested_amount,
-  bool refreshed)
+  const struct TALER_Amount *requested_amount)
 {
   struct RecoupContext pc;
   const struct TEH_DenominationKey *dk;
-  struct TALER_CoinPubHash c_hash;
   MHD_RESULT mret;
 
   /* check denomination exists and is in recoup mode */
@@ -324,7 +200,6 @@ verify_and_execute_recoup (
     return TEH_RESPONSE_reply_expired_denom_pub_hash (
       connection,
       &coin->denom_pub_hash,
-      GNUNET_TIME_timestamp_get (),
       TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
       "RECOUP");
   }
@@ -334,7 +209,6 @@ verify_and_execute_recoup (
     return TEH_RESPONSE_reply_expired_denom_pub_hash (
       connection,
       &coin->denom_pub_hash,
-      GNUNET_TIME_timestamp_get (),
       TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
       "RECOUP");
   }
@@ -344,23 +218,21 @@ verify_and_execute_recoup (
     return TEH_RESPONSE_reply_expired_denom_pub_hash (
       connection,
       &coin->denom_pub_hash,
-      GNUNET_TIME_timestamp_get (),
       TALER_EC_EXCHANGE_RECOUP_NOT_ELIGIBLE,
       "RECOUP");
   }
 
-  pc.value = dk->meta.value;
-
   /* check denomination signature */
   if (GNUNET_YES !=
       TALER_test_coin_valid (coin,
                              &dk->denom_pub))
   {
-    TALER_LOG_WARNING ("Invalid coin passed for recoup\n");
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_FORBIDDEN,
-                                       TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
-                                       NULL);
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_FORBIDDEN,
+      TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
+      NULL);
   }
 
   /* check recoup request signature */
@@ -372,15 +244,17 @@ verify_and_execute_recoup (
                                   coin_sig))
   {
     GNUNET_break_op (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_FORBIDDEN,
-                                       TALER_EC_EXCHANGE_RECOUP_SIGNATURE_INVALID,
-                                       NULL);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_FORBIDDEN,
+      TALER_EC_EXCHANGE_RECOUP_SIGNATURE_INVALID,
+      NULL);
   }
 
   {
     void *coin_ev;
     size_t coin_ev_size;
+    struct TALER_CoinPubHash c_hash;
 
     if (GNUNET_OK !=
         TALER_denom_blind (&dk->denom_pub,
@@ -392,10 +266,11 @@ verify_and_execute_recoup (
                            &coin_ev_size))
     {
       GNUNET_break (0);
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_EXCHANGE_RECOUP_BLINDING_FAILED,
-                                         NULL);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_INTERNAL_SERVER_ERROR,
+        TALER_EC_EXCHANGE_RECOUP_BLINDING_FAILED,
+        NULL);
     }
     TALER_coin_ev_hash (coin_ev,
                         coin_ev_size,
@@ -406,7 +281,6 @@ verify_and_execute_recoup (
   pc.coin_sig = coin_sig;
   pc.coin_bks = coin_bks;
   pc.coin = coin;
-  pc.refreshed = refreshed;
   pc.requested_amount = requested_amount;
 
   {
@@ -416,6 +290,7 @@ verify_and_execute_recoup (
     /* make sure coin is 'known' in database */
     qs = TEH_make_coin_known (coin,
                               connection,
+                              &pc.known_coin_id,
                               &mhd_ret);
     /* no transaction => no serialization failures should be possible */
     GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
@@ -426,35 +301,18 @@ verify_and_execute_recoup (
   {
     enum GNUNET_DB_QueryStatus qs;
 
-    if (pc.refreshed)
-    {
-      qs = TEH_plugin->get_old_coin_by_h_blind (TEH_plugin->cls,
-                                                &pc.h_blind,
-                                                &pc.target.old_coin_pub);
-      if (0 > qs)
-      {
-        GNUNET_break (0);
-        return TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_INTERNAL_SERVER_ERROR,
-          TALER_EC_GENERIC_DB_FETCH_FAILED,
-          "old coin by h_blind");
-      }
-    }
-    else
+    qs = TEH_plugin->get_reserve_by_h_blind (TEH_plugin->cls,
+                                             &pc.h_blind,
+                                             &pc.reserve_pub,
+                                             &pc.reserve_out_serial_id);
+    if (0 > qs)
     {
-      qs = TEH_plugin->get_reserve_by_h_blind (TEH_plugin->cls,
-                                               &pc.h_blind,
-                                               &pc.target.reserve_pub);
-      if (0 > qs)
-      {
-        GNUNET_break (0);
-        return TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_INTERNAL_SERVER_ERROR,
-          TALER_EC_GENERIC_DB_FETCH_FAILED,
-          "reserve by h_blind");
-      }
+      GNUNET_break (0);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_INTERNAL_SERVER_ERROR,
+        TALER_EC_GENERIC_DB_FETCH_FAILED,
+        "get_reserve_by_h_blind");
     }
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
     {
@@ -483,21 +341,11 @@ verify_and_execute_recoup (
       return mhd_ret;
   }
   /* Recoup succeeded, return result */
-  return (refreshed)
-         ? TALER_MHD_REPLY_JSON_PACK (connection,
-                                      MHD_HTTP_OK,
-                                      GNUNET_JSON_pack_data_auto (
-                                        "old_coin_pub",
-                                        &pc.target.old_coin_pub),
-                                      GNUNET_JSON_pack_bool ("refreshed",
-                                                             true))
-         : TALER_MHD_REPLY_JSON_PACK (connection,
-                                      MHD_HTTP_OK,
-                                      GNUNET_JSON_pack_data_auto (
-                                        "reserve_pub",
-                                        &pc.target.reserve_pub),
-                                      GNUNET_JSON_pack_bool ("refreshed",
-                                                             false));
+  return TALER_MHD_REPLY_JSON_PACK (connection,
+                                    MHD_HTTP_OK,
+                                    GNUNET_JSON_pack_data_auto (
+                                      "reserve_pub",
+                                      &pc.reserve_pub));
 }
 
 
@@ -522,7 +370,6 @@ TEH_handler_recoup (struct MHD_Connection *connection,
   union TALER_DenominationBlindingKeyP coin_bks;
   struct TALER_CoinSpendSignatureP coin_sig;
   struct TALER_Amount amount;
-  bool refreshed = false;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
                                  &coin.denom_pub_hash),
@@ -535,12 +382,12 @@ TEH_handler_recoup (struct MHD_Connection *connection,
     TALER_JSON_spec_amount ("amount",
                             TEH_currency,
                             &amount),
-    GNUNET_JSON_spec_mark_optional (
-      GNUNET_JSON_spec_bool ("refreshed",
-                             &refreshed)),
     GNUNET_JSON_spec_end ()
   };
 
+  memset (&coin,
+          0,
+          sizeof (coin));
   coin.coin_pub = *coin_pub;
   ret = TALER_MHD_parse_json_data (connection,
                                    root,
@@ -556,8 +403,7 @@ TEH_handler_recoup (struct MHD_Connection *connection,
                                      &coin,
                                      &coin_bks,
                                      &coin_sig,
-                                     &amount,
-                                     refreshed);
+                                     &amount);
     GNUNET_JSON_parse_free (spec);
     return res;
   }
diff --git a/src/exchange/taler-exchange-httpd_refreshes_reveal.c b/src/exchange/taler-exchange-httpd_refreshes_reveal.c
index 36362a234..1cd28048b 100644
--- a/src/exchange/taler-exchange-httpd_refreshes_reveal.c
+++ b/src/exchange/taler-exchange-httpd_refreshes_reveal.c
@@ -36,13 +36,6 @@
  */
 #define MAX_FRESH_COINS 256
 
-/**
- * How often do we at most retry the reveal transaction sequence?
- * Twice should really suffice in all cases (as the possible conflict
- * cannot happen more than once).
- */
-#define MAX_REVEAL_RETRIES 2
-
 
 /**
  * Send a response for "/refreshes/$RCH/reveal".
@@ -53,10 +46,10 @@
  * @return a MHD result code
  */
 static MHD_RESULT
-reply_refreshes_reveal_success (struct MHD_Connection *connection,
-                                unsigned int num_freshcoins,
-                                const struct
-                                TALER_BlindedDenominationSignature *sigs)
+reply_refreshes_reveal_success (
+  struct MHD_Connection *connection,
+  unsigned int num_freshcoins,
+  const struct TALER_BlindedDenominationSignature *sigs)
 {
   json_t *list;
 
@@ -121,157 +114,34 @@ struct RevealContext
   const struct TALER_RefreshCoinData *rcds;
 
   /**
-   * Signatures over the link data (of type
-   * #TALER_SIGNATURE_WALLET_COIN_LINK)
-   */
-  const struct TALER_CoinSpendSignatureP *link_sigs;
-
-  /**
-   * Envelopes with the signatures to be returned.  Initially NULL.
-   */
-  struct TALER_BlindedDenominationSignature *ev_sigs;
-
-  /**
    * Size of the @e dks, @e rcds and @e ev_sigs arrays (if non-NULL).
    */
   unsigned int num_fresh_coins;
 
-  /**
-   * Result from preflight checks. #GNUNET_NO for no result,
-   * #GNUNET_YES if preflight found previous successful operation,
-   * #GNUNET_SYSERR if prefight check failed hard (and generated
-   * an MHD response already).
-   */
-  int preflight_ok;
-
 };
 
 
 /**
- * Function called with information about a refresh order we already
- * persisted.  Stores the result in @a cls so we don't do the calculation
- * again.
- *
- * @param cls closure with a `struct RevealContext`
- * @param num_freshcoins size of the @a rrcs array
- * @param rrcs array of @a num_freshcoins information about coins to be created
- * @param num_tprivs number of entries in @a tprivs, should be #TALER_CNC_KAPPA - 1
- * @param tprivs array of @e num_tprivs transfer private keys
- * @param tp transfer public key information
- */
-static void
-check_exists_cb (void *cls,
-                 uint32_t num_freshcoins,
-                 const struct TALER_EXCHANGEDB_RefreshRevealedCoin *rrcs,
-                 unsigned int num_tprivs,
-                 const struct TALER_TransferPrivateKeyP *tprivs,
-                 const struct TALER_TransferPublicKeyP *tp)
-{
-  struct RevealContext *rctx = cls;
-
-  if (0 == num_freshcoins)
-  {
-    GNUNET_break (0);
-    return;
-  }
-  /* This should be a database invariant for us */
-  GNUNET_break (TALER_CNC_KAPPA - 1 == num_tprivs);
-  /* Given that the $RCH value matched, we don't actually need to check these
-     values (we checked before). However, if a client repeats a request with
-     invalid values the 2nd time, that's a protocol violation we should at least
-     log (but it's safe to ignore it). */
-  GNUNET_break_op (0 ==
-                   GNUNET_memcmp (tp,
-                                  &rctx->gamma_tp));
-  GNUNET_break_op (0 ==
-                   memcmp (tprivs,
-                           &rctx->transfer_privs,
-                           sizeof (struct TALER_TransferPrivateKeyP)
-                           * num_tprivs));
-  /* We usually sign early (optimistic!), but in case we change that *and*
-     we do find the operation in the database, we could use this: */
-  if (NULL == rctx->ev_sigs)
-  {
-    rctx->ev_sigs = GNUNET_new_array (num_freshcoins,
-                                      struct TALER_BlindedDenominationSignature);
-    for (unsigned int i = 0; i<num_freshcoins; i++)
-      TALER_blinded_denom_sig_deep_copy (&rctx->ev_sigs[i],
-                                         &rrcs[i].coin_sig);
-  }
-}
-
-
-/**
- * Check if the "/refreshes/$RCH/reveal" request was already successful
- * before.  If so, just return the old result.
- *
- * @param cls closure of type `struct RevealContext`
- * @param connection MHD request which triggered the transaction
- * @param[out] mhd_ret set to MHD response status for @a connection,
- *             if transaction failed (!)
- * @return transaction status
- */
-static enum GNUNET_DB_QueryStatus
-refreshes_reveal_preflight (void *cls,
-                            struct MHD_Connection *connection,
-                            MHD_RESULT *mhd_ret)
-{
-  struct RevealContext *rctx = cls;
-  enum GNUNET_DB_QueryStatus qs;
-
-  /* Try to see if we already have given an answer before. */
-  qs = TEH_plugin->get_refresh_reveal (TEH_plugin->cls,
-                                       &rctx->rc,
-                                       &check_exists_cb,
-                                       rctx);
-  switch (qs)
-  {
-  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-    return qs; /* continue normal execution */
-  case GNUNET_DB_STATUS_SOFT_ERROR:
-    return qs;
-  case GNUNET_DB_STATUS_HARD_ERROR:
-    GNUNET_break (qs);
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                           "refresh reveal");
-    rctx->preflight_ok = GNUNET_SYSERR;
-    return GNUNET_DB_STATUS_HARD_ERROR;
-  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
-  default:
-    /* Hossa, already found our reply! */
-    GNUNET_assert (NULL != rctx->ev_sigs);
-    rctx->preflight_ok = GNUNET_YES;
-    return qs;
-  }
-}
-
-
-/**
- * Execute a "/refreshes/$RCH/reveal".  The client is revealing to us the
+ * Check client's revelation against the original commitment.
+ * The client is revealing to us the
  * transfer keys for @a #TALER_CNC_KAPPA-1 sets of coins.  Verify that the
  * revealed transfer keys would allow linkage to the blinded coins.
  *
- * IF it returns a non-error code, the transaction logic MUST
- * NOT queue a MHD response.  IF it returns an hard error, the
- * transaction logic MUST queue a MHD response and set @a mhd_ret.  IF
- * it returns the soft error code, the function MAY be called again to
- * retry and MUST not queue a MHD response.
+ * IF it returns #GNUNET_OK, the transaction logic MUST
+ * NOT queue a MHD response.  IF it returns an error, the
+ * transaction logic MUST queue a MHD response and set @a mhd_ret.
  *
- * @param cls closure of type `struct RevealContext`
+ * @param rctx our operation context
  * @param connection MHD request which triggered the transaction
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
- * @return transaction status
+ * @return #GNUNET_OK if commitment was OK
  */
-static enum GNUNET_DB_QueryStatus
-refreshes_reveal_transaction (void *cls,
-                              struct MHD_Connection *connection,
-                              MHD_RESULT *mhd_ret)
+static enum GNUNET_GenericReturnValue
+check_commitment (struct RevealContext *rctx,
+                  struct MHD_Connection *connection,
+                  MHD_RESULT *mhd_ret)
 {
-  struct RevealContext *rctx = cls;
-
   /* Verify commitment */
   {
     /* Note that the contents of rcs[melt.session.noreveal_index]
@@ -363,7 +233,7 @@ refreshes_reveal_transaction (void *cls,
           TALER_EC_EXCHANGE_REFRESHES_REVEAL_COMMITMENT_VIOLATION),
         GNUNET_JSON_pack_data_auto ("rc_expected",
                                     &rc_expected));
-      return GNUNET_DB_STATUS_HARD_ERROR;
+      return GNUNET_SYSERR;
     }
   } /* end of checking "rc_expected" */
 
@@ -390,7 +260,7 @@ refreshes_reveal_transaction (void *cls,
                                                MHD_HTTP_INTERNAL_SERVER_ERROR,
                                                TALER_EC_EXCHANGE_REFRESHES_REVEAL_COST_CALCULATION_OVERFLOW,
                                                NULL);
-        return GNUNET_DB_STATUS_HARD_ERROR;
+        return GNUNET_SYSERR;
       }
     }
     if (0 < TALER_amount_cmp (&refresh_cost,
@@ -401,60 +271,10 @@ refreshes_reveal_transaction (void *cls,
                                              MHD_HTTP_BAD_REQUEST,
                                              TALER_EC_EXCHANGE_REFRESHES_REVEAL_AMOUNT_INSUFFICIENT,
                                              NULL);
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-  }
-  return GNUNET_DB_STATUS_SUCCESS_NO_RESULTS;
-}
-
-
-/**
- * Persist result of a "/refreshes/$RCH/reveal" operation.
- *
- * @param cls closure of type `struct RevealContext`
- * @param connection MHD request which triggered the transaction
- * @param[out] mhd_ret set to MHD response status for @a connection,
- *             if transaction failed (!)
- * @return transaction status
- */
-static enum GNUNET_DB_QueryStatus
-refreshes_reveal_persist (void *cls,
-                          struct MHD_Connection *connection,
-                          MHD_RESULT *mhd_ret)
-{
-  struct RevealContext *rctx = cls;
-  enum GNUNET_DB_QueryStatus qs;
-
-  /* Persist operation result in DB */
-  {
-    struct TALER_EXCHANGEDB_RefreshRevealedCoin rrcs[rctx->num_fresh_coins];
-
-    for (unsigned int i = 0; i<rctx->num_fresh_coins; i++)
-    {
-      struct TALER_EXCHANGEDB_RefreshRevealedCoin *rrc = &rrcs[i];
-
-      rrc->denom_pub = rctx->dks[i]->denom_pub;
-      rrc->orig_coin_link_sig = rctx->link_sigs[i];
-      rrc->coin_ev = rctx->rcds[i].coin_ev;
-      rrc->coin_ev_size = rctx->rcds[i].coin_ev_size;
-      rrc->coin_sig = rctx->ev_sigs[i];
+      return GNUNET_SYSERR;
     }
-    qs = TEH_plugin->insert_refresh_reveal (TEH_plugin->cls,
-                                            &rctx->rc,
-                                            rctx->num_fresh_coins,
-                                            rrcs,
-                                            TALER_CNC_KAPPA - 1,
-                                            rctx->transfer_privs,
-                                            &rctx->gamma_tp);
   }
-  if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-  {
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GENERIC_DB_STORE_FAILED,
-                                           "refresh_reveal");
-  }
-  return qs;
+  return GNUNET_OK;
 }
 
 
@@ -481,9 +301,18 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
   struct TALER_DenominationHash dk_h[num_fresh_coins];
   struct TALER_RefreshCoinData rcds[num_fresh_coins];
   struct TALER_CoinSpendSignatureP link_sigs[num_fresh_coins];
-  enum GNUNET_GenericReturnValue res;
+  struct TALER_BlindedDenominationSignature ev_sigs[num_fresh_coins];
   MHD_RESULT ret;
   struct TEH_KeyStateHandle *ksh;
+  uint64_t melt_serial_id;
+
+  rctx->num_fresh_coins = num_fresh_coins;
+  memset (dks, 0, sizeof (dks));
+  memset (rcds, 0, sizeof (rcds));
+  memset (link_sigs, 0, sizeof (link_sigs));
+  memset (ev_sigs, 0, sizeof (ev_sigs));
+  rctx->dks = dks;
+  rctx->rcds = rcds;
 
   ksh = TEH_keys_get_state ();
   if (NULL == ksh)
@@ -501,7 +330,7 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
                                    &dk_h[i]),
       GNUNET_JSON_spec_end ()
     };
-    MHD_RESULT mret;
+    enum GNUNET_GenericReturnValue res;
 
     res = TALER_MHD_parse_json_array (connection,
                                       new_denoms_h_json,
@@ -509,15 +338,13 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
                                       i,
                                       -1);
     if (GNUNET_OK != res)
-    {
       return (GNUNET_NO == res) ? MHD_YES : MHD_NO;
-    }
     dks[i] = TEH_keys_denomination_by_hash2 (ksh,
                                              &dk_h[i],
                                              connection,
-                                             &mret);
+                                             &ret);
     if (NULL == dks[i])
-      return mret;
+      return ret;
 
     if (GNUNET_TIME_absolute_is_past (dks[i]->meta.expire_withdraw.abs_time))
     {
@@ -525,7 +352,6 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         connection,
         &dk_h[i],
-        GNUNET_TIME_timestamp_get (),
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
         "REVEAL");
     }
@@ -535,7 +361,6 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         connection,
         &dk_h[i],
-        GNUNET_TIME_timestamp_get (),
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
         "REVEAL");
     }
@@ -560,6 +385,7 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
                                 &rcd->coin_ev_size),
       GNUNET_JSON_spec_end ()
     };
+    enum GNUNET_GenericReturnValue res;
 
     res = TALER_MHD_parse_json_array (connection,
                                       coin_evs,
@@ -582,7 +408,8 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
     if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT !=
         (qs = TEH_plugin->get_melt (TEH_plugin->cls,
                                     &rctx->rc,
-                                    &rctx->melt)))
+                                    &rctx->melt,
+                                    &melt_serial_id)))
     {
       switch (qs)
       {
@@ -609,8 +436,6 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
       }
       goto cleanup;
     }
-    /* Obtain basic information about the refresh operation and what
-       gamma we committed to. */
     if (rctx->melt.session.noreveal_index >= TALER_CNC_KAPPA)
     {
       GNUNET_break (0);
@@ -625,9 +450,11 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
   for (unsigned int i = 0; i<num_fresh_coins; i++)
   {
     struct GNUNET_JSON_Specification link_spec[] = {
-      GNUNET_JSON_spec_fixed_auto (NULL, &link_sigs[i]),
+      GNUNET_JSON_spec_fixed_auto (NULL,
+                                   &link_sigs[i]),
       GNUNET_JSON_spec_end ()
     };
+    enum GNUNET_GenericReturnValue res;
 
     res = TALER_MHD_parse_json_array (connection,
                                       link_sigs_json,
@@ -656,27 +483,26 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
     }
   }
 
-  rctx->num_fresh_coins = num_fresh_coins;
-  rctx->rcds = rcds;
-  rctx->dks = dks;
-  rctx->link_sigs = link_sigs;
+  if (GNUNET_OK !=
+      check_commitment (rctx,
+                        connection,
+                        &ret))
+    goto cleanup;
+
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Optimistically creating %u signatures\n",
+              "Creating %u signatures\n",
               (unsigned int) rctx->num_fresh_coins);
   /* sign _early_ (optimistic!) to keep out of transaction scope! */
-  rctx->ev_sigs = GNUNET_new_array (rctx->num_fresh_coins,
-                                    struct TALER_BlindedDenominationSignature);
-  // FIXME: this is sequential, modify logic to enable parallel signing!
   for (unsigned int i = 0; i<rctx->num_fresh_coins; i++)
   {
     enum TALER_ErrorCode ec = TALER_EC_NONE;
 
-    rctx->ev_sigs[i]
+    ev_sigs[i]
       = TEH_keys_denomination_sign (
           &dk_h[i],
-          rctx->rcds[i].coin_ev,
-          rctx->rcds[i].coin_ev_size,
+          rcds[i].coin_ev,
+          rcds[i].coin_ev_size,
           &ec);
     if (TALER_EC_NONE != ec)
     {
@@ -687,81 +513,50 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
       goto cleanup;
     }
   }
-
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Signatures ready, starting DB interaction\n");
-  /* We try the three transactions a few times, as theoretically
-     the pre-check might be satisfied by a concurrent transaction
-     voiding our final commit due to uniqueness violation; naturally,
-     on hard errors we exit immediately */
-  for (unsigned int retries = 0; retries < MAX_REVEAL_RETRIES; retries++)
+  /* Persist operation result in DB */
   {
-    /* do transactional work */
-    rctx->preflight_ok = GNUNET_NO;
-    if ( (GNUNET_OK ==
-          TEH_DB_run_transaction (connection,
-                                  "reveal pre-check",
-                                  TEH_MT_REVEAL_PRECHECK,
-                                  &ret,
-                                  &refreshes_reveal_preflight,
-                                  rctx)) &&
-         (GNUNET_YES == rctx->preflight_ok) )
+    struct TALER_EXCHANGEDB_RefreshRevealedCoin rrcs[rctx->num_fresh_coins];
+    enum GNUNET_DB_QueryStatus qs;
+
+    for (unsigned int i = 0; i<rctx->num_fresh_coins; i++)
     {
-      /* Generate final (positive) response */
-      GNUNET_assert (NULL != rctx->ev_sigs);
-      ret = reply_refreshes_reveal_success (connection,
-                                            num_fresh_coins,
-                                            rctx->ev_sigs);
-      GNUNET_break (MHD_NO != ret);
-      goto cleanup;   /* aka 'break' */
+      struct TALER_EXCHANGEDB_RefreshRevealedCoin *rrc = &rrcs[i];
+
+      rrc->h_denom_pub = dk_h[i];
+      rrc->orig_coin_link_sig = link_sigs[i];
+      rrc->coin_ev = rcds[i].coin_ev;
+      rrc->coin_ev_size = rcds[i].coin_ev_size;
+      rrc->coin_sig = ev_sigs[i];
     }
-    if (GNUNET_SYSERR == rctx->preflight_ok)
+    qs = TEH_plugin->insert_refresh_reveal (TEH_plugin->cls,
+                                            melt_serial_id,
+                                            num_fresh_coins,
+                                            rrcs,
+                                            TALER_CNC_KAPPA - 1,
+                                            rctx->transfer_privs,
+                                            &rctx->gamma_tp);
+    if (0 > qs)
     {
       GNUNET_break (0);
-      goto cleanup;   /* aka 'break' */
-    }
-    if (GNUNET_OK !=
-        TEH_DB_run_transaction (connection,
-                                "run reveal",
-                                TEH_MT_REVEAL,
-                                &ret,
-                                &refreshes_reveal_transaction,
-                                rctx))
-    {
-      /* reveal failed, too bad */
-      GNUNET_break_op (0);
-      goto cleanup;   /* aka 'break' */
-    }
-    if (GNUNET_OK ==
-        TEH_DB_run_transaction (connection,
-                                "persist reveal",
-                                TEH_MT_REVEAL_PERSIST,
-                                &ret,
-                                &refreshes_reveal_persist,
-                                rctx))
-    {
-      /* Generate final (positive) response */
-      GNUNET_assert (NULL != rctx->ev_sigs);
-      ret = reply_refreshes_reveal_success (connection,
-                                            num_fresh_coins,
-                                            rctx->ev_sigs);
-      break;
+      ret = TALER_MHD_reply_with_error (connection,
+                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                        TALER_EC_GENERIC_DB_STORE_FAILED,
+                                        "insert_refresh_reveal");
+      goto cleanup;
     }
-    /* If we get here, the final transaction failed, possibly
-       due to a conflict between the pre-flight and us persisting
-       the result, so we go again. */
-  }   /* end for (retries...) */
+  }
 
+  /* Generate final (positive) response */
+  ret = reply_refreshes_reveal_success (connection,
+                                        num_fresh_coins,
+                                        ev_sigs);
 cleanup:
   GNUNET_break (MHD_NO != ret);
   /* free resources */
-  if (NULL != rctx->ev_sigs)
-  {
-    for (unsigned int i = 0; i<num_fresh_coins; i++)
-      TALER_blinded_denom_sig_free (&rctx->ev_sigs[i]);
-    GNUNET_free (rctx->ev_sigs);
-    rctx->ev_sigs = NULL; /* just to be safe... */
-  }
+  for (unsigned int i = 0; i<num_fresh_coins; i++)
+    TALER_blinded_denom_sig_free (&ev_sigs[i]);
   for (unsigned int i = 0; i<num_fresh_coins; i++)
     GNUNET_free (rcds[i].coin_ev);
   return ret;
@@ -828,7 +623,8 @@ handle_refreshes_reveal_json (struct MHD_Connection *connection,
   for (unsigned int i = 0; i<num_tprivs; i++)
   {
     struct GNUNET_JSON_Specification trans_spec[] = {
-      GNUNET_JSON_spec_fixed_auto (NULL, &rctx->transfer_privs[i]),
+      GNUNET_JSON_spec_fixed_auto (NULL,
+                                   &rctx->transfer_privs[i]),
       GNUNET_JSON_spec_end ()
     };
     enum GNUNET_GenericReturnValue res;
@@ -861,11 +657,16 @@ TEH_handler_reveal (struct TEH_RequestContext *rc,
   json_t *new_denoms_h;
   struct RevealContext rctx;
   struct GNUNET_JSON_Specification spec[] = {
-    GNUNET_JSON_spec_fixed_auto ("transfer_pub", &rctx.gamma_tp),
-    GNUNET_JSON_spec_json ("transfer_privs", &transfer_privs),
-    GNUNET_JSON_spec_json ("link_sigs", &link_sigs),
-    GNUNET_JSON_spec_json ("coin_evs", &coin_evs),
-    GNUNET_JSON_spec_json ("new_denoms_h", &new_denoms_h),
+    GNUNET_JSON_spec_fixed_auto ("transfer_pub",
+                                 &rctx.gamma_tp),
+    GNUNET_JSON_spec_json ("transfer_privs",
+                           &transfer_privs),
+    GNUNET_JSON_spec_json ("link_sigs",
+                           &link_sigs),
+    GNUNET_JSON_spec_json ("coin_evs",
+                           &coin_evs),
+    GNUNET_JSON_spec_json ("new_denoms_h",
+                           &new_denoms_h),
     GNUNET_JSON_spec_end ()
   };
 
diff --git a/src/exchange/taler-exchange-httpd_refund.c b/src/exchange/taler-exchange-httpd_refund.c
index a1ef50a32..a3b066280 100644
--- a/src/exchange/taler-exchange-httpd_refund.c
+++ b/src/exchange/taler-exchange-httpd_refund.c
@@ -82,6 +82,28 @@ reply_refund_success (struct MHD_Connection *connection,
 
 
 /**
+ * Closure for refund_transaction().
+ */
+struct RefundContext
+{
+  /**
+   * Details about the deposit operation.
+   */
+  const struct TALER_EXCHANGEDB_Refund *refund;
+
+  /**
+   * Deposit fee of the coin.
+   */
+  struct TALER_Amount deposit_fee;
+
+  /**
+   * Unique ID of the coin in known_coins.
+   */
+  uint64_t known_coin_id;
+};
+
+
+/**
  * Execute a "/refund" transaction.  Returns a confirmation that the
  * refund was successful, or a failure if we are not aware of a
  * matching /deposit or if it is too late to do the refund.
@@ -103,255 +125,67 @@ refund_transaction (void *cls,
                     struct MHD_Connection *connection,
                     MHD_RESULT *mhd_ret)
 {
-  const struct TALER_EXCHANGEDB_Refund *refund = cls;
-  struct TALER_EXCHANGEDB_TransactionList *tl; /* head of original list */
-  struct TALER_EXCHANGEDB_TransactionList *tlx; /* head of sublist that applies to merchant and contract */
-  struct TALER_EXCHANGEDB_TransactionList *tln; /* next element, during iteration */
-  struct TALER_EXCHANGEDB_TransactionList *tlp; /* previous element in 'tl' list, during iteration */
+  struct RefundContext *rctx = cls;
+  const struct TALER_EXCHANGEDB_Refund *refund = rctx->refund;
   enum GNUNET_DB_QueryStatus qs;
-  bool deposit_found; /* deposit_total initialized? */
-  bool refund_found; /* refund_total initialized? */
-  struct TALER_Amount deposit_total;
-  struct TALER_Amount refund_total;
-
-  tl = NULL;
-  qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                          &refund->coin.coin_pub,
-                                          GNUNET_NO,
-                                          &tl);
+  bool not_found;
+  bool refund_ok;
+  bool conflict;
+  bool gone;
+
+  /* Finally, store new refund data */
+  qs = TEH_plugin->do_refund (TEH_plugin->cls,
+                              refund,
+                              &rctx->deposit_fee,
+                              rctx->known_coin_id,
+                              &not_found,
+                              &refund_ok,
+                              &gone,
+                              &conflict);
   if (0 > qs)
   {
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
       *mhd_ret = TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_INTERNAL_SERVER_ERROR,
                                              TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                             "coin transactions");
+                                             "do refund");
     return qs;
   }
-  deposit_found = false;
-  refund_found = false;
-  tlx = NULL; /* relevant subset of transactions */
-  tln = NULL;
-  tlp = NULL;
-  for (struct TALER_EXCHANGEDB_TransactionList *tli = tl;
-       NULL != tli;
-       tli = tln)
+
+  if (gone)
   {
-    tln = tli->next;
-    switch (tli->type)
-    {
-    case TALER_EXCHANGEDB_TT_DEPOSIT:
-      {
-        const struct TALER_EXCHANGEDB_DepositListEntry *dep;
-
-        dep = tli->details.deposit;
-        if ( (0 == GNUNET_memcmp (&dep->merchant_pub,
-                                  &refund->details.merchant_pub)) &&
-             (0 == GNUNET_memcmp (&dep->h_contract_terms,
-                                  &refund->details.h_contract_terms)) )
-        {
-          /* check if we already send the money for this /deposit */
-          if (dep->done)
-          {
-            TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                    tlx);
-            TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                    tln);
-            /* money was already transferred to merchant, can no longer refund */
-            *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                                   MHD_HTTP_GONE,
-                                                   TALER_EC_EXCHANGE_REFUND_MERCHANT_ALREADY_PAID,
-                                                   NULL);
-            return GNUNET_DB_STATUS_HARD_ERROR;
-          }
-
-          /* deposit applies and was not yet wired; add to total (it is NOT
-             the case that multiple deposits of the same coin for the same
-             contract are really allowed (see UNIQUE constraint on 'deposits'
-             table), but in case this changes we tolerate it with this code
-             anyway). *///
-          if (deposit_found)
-          {
-            GNUNET_assert (0 <=
-                           TALER_amount_add (&deposit_total,
-                                             &deposit_total,
-                                             &dep->amount_with_fee));
-          }
-          else
-          {
-            deposit_total = dep->amount_with_fee;
-            deposit_found = true;
-          }
-          /* move 'tli' from 'tl' to 'tlx' list */
-          if (NULL == tlp)
-            tl = tln;
-          else
-            tlp->next = tln;
-          tli->next = tlx;
-          tlx = tli;
-          break;
-        }
-        else
-        {
-          tlp = tli;
-        }
-        break;
-      }
-    case TALER_EXCHANGEDB_TT_MELT:
-      /* Melts cannot be refunded, ignore here */
-      break;
-    case TALER_EXCHANGEDB_TT_REFUND:
-      {
-        const struct TALER_EXCHANGEDB_RefundListEntry *ref;
-
-        ref = tli->details.refund;
-        if ( (0 != GNUNET_memcmp (&ref->merchant_pub,
-                                  &refund->details.merchant_pub)) ||
-             (0 != GNUNET_memcmp (&ref->h_contract_terms,
-                                  &refund->details.h_contract_terms)) )
-        {
-          tlp = tli;
-          break; /* refund does not apply to our transaction */
-        }
-        /* Check if existing refund request matches in everything but the amount */
-        if ( (ref->rtransaction_id ==
-              refund->details.rtransaction_id) &&
-             (0 != TALER_amount_cmp (&ref->refund_amount,
-                                     &refund->details.refund_amount)) )
-        {
-          /* Generate precondition failed response, with ONLY the conflicting entry */
-          TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                  tlx);
-          TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                  tln);
-          tli->next = NULL;
-          *mhd_ret = TALER_MHD_REPLY_JSON_PACK (
-            connection,
-            MHD_HTTP_PRECONDITION_FAILED,
-            TALER_JSON_pack_amount ("detail",
-                                    &ref->refund_amount),
-            TALER_JSON_pack_ec (TALER_EC_EXCHANGE_REFUND_INCONSISTENT_AMOUNT),
-            GNUNET_JSON_pack_array_steal ("history",
-                                          TEH_RESPONSE_compile_transaction_history (
-                                            &refund->coin.coin_pub,
-                                            tli)));
-          TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                  tli);
-          return GNUNET_DB_STATUS_HARD_ERROR;
-        }
-        /* Check if existing refund request matches in everything including the amount */
-        if ( (ref->rtransaction_id ==
-              refund->details.rtransaction_id) &&
-             (0 == TALER_amount_cmp (&ref->refund_amount,
-                                     &refund->details.refund_amount)) )
-        {
-          /* we can blanketly approve, as this request is identical to one
-             we saw before */
-          *mhd_ret = reply_refund_success (connection,
-                                           &refund->coin.coin_pub,
-                                           ref);
-          TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                  tlx);
-          TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                                  tl);
-          /* we still abort the transaction, as there is nothing to be
-             committed! */
-          return GNUNET_DB_STATUS_HARD_ERROR;
-        }
-
-        /* We have another refund, that relates, add to total */
-        if (refund_found)
-        {
-          GNUNET_assert (0 <=
-                         TALER_amount_add (&refund_total,
-                                           &refund_total,
-                                           &ref->refund_amount));
-        }
-        else
-        {
-          refund_total = ref->refund_amount;
-          refund_found = true;
-        }
-        /* move 'tli' from 'tl' to 'tlx' list */
-        if (NULL == tlp)
-          tl = tln;
-        else
-          tlp->next = tln;
-        tli->next = tlx;
-        tlx = tli;
-        break;
-      }
-    case TALER_EXCHANGEDB_TT_OLD_COIN_RECOUP:
-      /* Recoups cannot be refunded, ignore here */
-      break;
-    case TALER_EXCHANGEDB_TT_RECOUP:
-      /* Recoups cannot be refunded, ignore here */
-      break;
-    case TALER_EXCHANGEDB_TT_RECOUP_REFRESH:
-      /* Recoups cannot be refunded, ignore here */
-      break;
-    }
+    *mhd_ret = TALER_MHD_reply_with_error (connection,
+                                           MHD_HTTP_GONE,
+                                           TALER_EC_EXCHANGE_REFUND_MERCHANT_ALREADY_PAID,
+                                           NULL);
+    return GNUNET_DB_STATUS_HARD_ERROR;
   }
-  /* no need for 'tl' anymore, everything we may still care about is in tlx now */
-  TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                          tl);
-  /* handle if deposit was NOT found */
-  if (! deposit_found)
+  if (conflict)
+  {
+    TEH_plugin->rollback (TEH_plugin->cls);
+    *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (
+      connection,
+      TALER_EC_EXCHANGE_REFUND_INCONSISTENT_AMOUNT,
+      &refund->coin.coin_pub);
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  }
+  if (not_found)
   {
-    TALER_LOG_WARNING ("Deposit to /refund was not found\n");
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tlx);
     *mhd_ret = TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_NOT_FOUND,
                                            TALER_EC_EXCHANGE_REFUND_DEPOSIT_NOT_FOUND,
                                            NULL);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
-
-  /* check total refund amount is sufficiently low */
-  if (refund_found)
-    GNUNET_break (0 <=
-                  TALER_amount_add (&refund_total,
-                                    &refund_total,
-                                    &refund->details.refund_amount));
-  else
-    refund_total = refund->details.refund_amount;
-
-  if (1 == TALER_amount_cmp (&refund_total,
-                             &deposit_total) )
+  if (! refund_ok)
   {
-    *mhd_ret = TALER_MHD_REPLY_JSON_PACK (
+    TEH_plugin->rollback (TEH_plugin->cls);
+    *mhd_ret = TEH_RESPONSE_reply_coin_insufficient_funds (
       connection,
-      MHD_HTTP_CONFLICT,
-      GNUNET_JSON_pack_string ("detail",
-                               "total amount refunded exceeds total amount deposited for this coin"),
-      TALER_JSON_pack_ec (
-        TALER_EC_EXCHANGE_REFUND_CONFLICT_DEPOSIT_INSUFFICIENT),
-      GNUNET_JSON_pack_array_steal ("history",
-                                    TEH_RESPONSE_compile_transaction_history (
-                                      &refund->coin.coin_pub,
-                                      tlx)));
-    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                            tlx);
+      TALER_EC_EXCHANGE_REFUND_CONFLICT_DEPOSIT_INSUFFICIENT,
+      &refund->coin.coin_pub);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
-  TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
-                                          tlx);
-
-
-  /* Finally, store new refund data */
-  qs = TEH_plugin->insert_refund (TEH_plugin->cls,
-                                  refund);
-  if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-  {
-    TALER_LOG_WARNING ("Failed to store /refund information in database\n");
-    *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GENERIC_DB_STORE_FAILED,
-                                           "refund");
-    return qs;
-  }
-  /* Success or soft failure */
   return qs;
 }
 
@@ -371,7 +205,11 @@ verify_and_execute_refund (struct MHD_Connection *connection,
                            struct TALER_EXCHANGEDB_Refund *refund)
 {
   struct TALER_DenominationHash denom_hash;
+  struct RefundContext rctx = {
+    .refund = refund
+  };
 
+  // FIXME: move to libtalerutil!
   {
     struct TALER_RefundRequestPS rr = {
       .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND),
@@ -404,6 +242,7 @@ verify_and_execute_refund (struct MHD_Connection *connection,
 
     qs = TEH_plugin->get_coin_denomination (TEH_plugin->cls,
                                             &refund->coin.coin_pub,
+                                            &rctx.known_coin_id,
                                             &denom_hash);
     if (0 > qs)
     {
@@ -438,6 +277,7 @@ verify_and_execute_refund (struct MHD_Connection *connection,
       return mret;
     }
     refund->details.refund_fee = dk->meta.fee_refund;
+    rctx.deposit_fee = dk->meta.fee_deposit;
   }
 
   /* Finally run the actual transaction logic */
@@ -450,7 +290,7 @@ verify_and_execute_refund (struct MHD_Connection *connection,
                                 TEH_MT_OTHER,
                                 &mhd_ret,
                                 &refund_transaction,
-                                (void *) refund))
+                                &rctx))
     {
       return mhd_ret;
     }
diff --git a/src/exchange/taler-exchange-httpd_responses.c b/src/exchange/taler-exchange-httpd_responses.c
index 8c24efc9d..5739e6709 100644
--- a/src/exchange/taler-exchange-httpd_responses.c
+++ b/src/exchange/taler-exchange-httpd_responses.c
@@ -122,25 +122,15 @@ TEH_RESPONSE_compile_transaction_history (
       {
         const struct TALER_EXCHANGEDB_MeltListEntry *melt =
           pos->details.melt;
-        struct TALER_RefreshMeltCoinAffirmationPS ms = {
-          .purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_MELT),
-          .purpose.size = htonl (sizeof (ms)),
-          .rc = melt->rc,
-          .h_denom_pub = melt->h_denom_pub,
-          .coin_pub = *coin_pub
-        };
 
-        TALER_amount_hton (&ms.amount_with_fee,
-                           &melt->amount_with_fee);
-        TALER_amount_hton (&ms.melt_fee,
-                           &melt->melt_fee);
 #if ENABLE_SANITY_CHECKS
-        /* internal sanity check before we hand out a bogus sig... */
         if (GNUNET_OK !=
-            GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_MELT,
-                                        &ms,
-                                        &melt->coin_sig.eddsa_signature,
-                                        &coin_pub->eddsa_pub))
+            TALER_wallet_melt_verify (&melt->amount_with_fee,
+                                      &melt->melt_fee,
+                                      &melt->rc,
+                                      &melt->h_denom_pub,
+                                      coin_pub,
+                                      &melt->coin_sig))
         {
           GNUNET_break (0);
           json_decref (history);
@@ -175,6 +165,7 @@ TEH_RESPONSE_compile_transaction_history (
         const struct TALER_EXCHANGEDB_RefundListEntry *refund =
           pos->details.refund;
         struct TALER_Amount value;
+        // FIXME: move to libtalerutil!
         struct TALER_RefundRequestPS rr = {
           .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND),
           .purpose.size = htonl (sizeof (rr)),
@@ -461,13 +452,14 @@ MHD_RESULT
 TEH_RESPONSE_reply_expired_denom_pub_hash (
   struct MHD_Connection *connection,
   const struct TALER_DenominationHash *dph,
-  struct GNUNET_TIME_Timestamp now,
   enum TALER_ErrorCode ec,
   const char *oper)
 {
   struct TALER_ExchangePublicKeyP epub;
   struct TALER_ExchangeSignatureP esig;
   enum TALER_ErrorCode ecr;
+  struct GNUNET_TIME_Timestamp now
+    = GNUNET_TIME_timestamp_get ();
   struct TALER_DenominationExpiredAffirmationPS dua = {
     .purpose.size = htonl (sizeof (dua)),
     .purpose.purpose = htonl (
@@ -525,13 +517,31 @@ MHD_RESULT
 TEH_RESPONSE_reply_coin_insufficient_funds (
   struct MHD_Connection *connection,
   enum TALER_ErrorCode ec,
-  const struct TALER_CoinSpendPublicKeyP *coin_pub,
-  const struct TALER_EXCHANGEDB_TransactionList *tl)
+  const struct TALER_CoinSpendPublicKeyP *coin_pub)
 {
+  struct TALER_EXCHANGEDB_TransactionList *tl;
+  enum GNUNET_DB_QueryStatus qs;
   json_t *history;
 
+  // FIXME: maybe start read-committed transaction here?
+  // => check all callers (that they aborted already!)
+  qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
+                                          coin_pub,
+                                          GNUNET_NO,
+                                          &tl);
+  if (0 > qs)
+  {
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_FETCH_FAILED,
+      NULL);
+  }
+
   history = TEH_RESPONSE_compile_transaction_history (coin_pub,
                                                       tl);
+  TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
+                                          tl);
   if (NULL == history)
   {
     GNUNET_break (0);
@@ -542,7 +552,7 @@ TEH_RESPONSE_reply_coin_insufficient_funds (
   }
   return TALER_MHD_REPLY_JSON_PACK (
     connection,
-    MHD_HTTP_CONFLICT,
+    TALER_ErrorCode_get_http_status_safe (ec),
     TALER_JSON_pack_ec (ec),
     GNUNET_JSON_pack_array_steal ("history",
                                   history));
diff --git a/src/exchange/taler-exchange-httpd_responses.h b/src/exchange/taler-exchange-httpd_responses.h
index e15901120..db2286ffa 100644
--- a/src/exchange/taler-exchange-httpd_responses.h
+++ b/src/exchange/taler-exchange-httpd_responses.h
@@ -67,7 +67,6 @@ TEH_RESPONSE_reply_unknown_denom_pub_hash (
  *
  * @param connection connection to the client
  * @param dph denomination public key hash
- * @param now timestamp to use
  * @param ec error code to use
  * @param oper name of the operation that is not allowed at this time
  * @return MHD result code
@@ -76,7 +75,6 @@ MHD_RESULT
 TEH_RESPONSE_reply_expired_denom_pub_hash (
   struct MHD_Connection *connection,
   const struct TALER_DenominationHash *dph,
-  struct GNUNET_TIME_Timestamp now,
   enum TALER_ErrorCode ec,
   const char *oper);
 
@@ -90,15 +88,13 @@ TEH_RESPONSE_reply_expired_denom_pub_hash (
  * @param connection connection to the client
  * @param ec error code to return
  * @param coin_pub public key of the coin
- * @param tl transaction list to use to build reply
  * @return MHD result code
  */
 MHD_RESULT
 TEH_RESPONSE_reply_coin_insufficient_funds (
   struct MHD_Connection *connection,
   enum TALER_ErrorCode ec,
-  const struct TALER_CoinSpendPublicKeyP *coin_pub,
-  const struct TALER_EXCHANGEDB_TransactionList *tl);
+  const struct TALER_CoinSpendPublicKeyP *coin_pub);
 
 
 /**
diff --git a/src/exchange/taler-exchange-httpd_withdraw.c b/src/exchange/taler-exchange-httpd_withdraw.c
index dfd10b5e4..2e53803a9 100644
--- a/src/exchange/taler-exchange-httpd_withdraw.c
+++ b/src/exchange/taler-exchange-httpd_withdraw.c
@@ -94,7 +94,7 @@ struct WithdrawContext
   /**
    * Blinded planchet.
    */
-  char *blinded_msg;
+  void *blinded_msg;
 
   /**
    * Number of bytes in @e blinded_msg.
@@ -141,6 +141,7 @@ withdraw_transaction (void *cls,
   bool found = false;
   bool balance_ok = false;
   struct GNUNET_TIME_Timestamp now;
+  uint64_t ruuid;
 
   now = GNUNET_TIME_timestamp_get ();
   wc->collectable.reserve_pub = wc->wsrd.reserve_pub;
@@ -150,7 +151,8 @@ withdraw_transaction (void *cls,
                                 now,
                                 &found,
                                 &balance_ok,
-                                &wc->kyc);
+                                &wc->kyc,
+                                &ruuid);
   if (0 > qs)
   {
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
@@ -174,6 +176,7 @@ withdraw_transaction (void *cls,
     struct TALER_Amount balance;
 
     TEH_plugin->rollback (TEH_plugin->cls);
+    // FIXME: maybe start read-committed here?
     if (GNUNET_OK !=
         TEH_plugin->start (TEH_plugin->cls,
                            "get_reserve_history on insufficient balance"))
@@ -232,7 +235,7 @@ withdraw_transaction (void *cls,
 
     qs2 = TEH_plugin->do_withdraw_limit_check (
       TEH_plugin->cls,
-      &wc->collectable.reserve_pub,
+      ruuid,
       GNUNET_TIME_absolute_subtract (now.abs_time,
                                      TEH_kyc_config.withdraw_period),
       &TEH_kyc_config.withdraw_limit,
@@ -249,6 +252,7 @@ withdraw_transaction (void *cls,
     }
     if (! below_limit)
     {
+      TEH_plugin->rollback (TEH_plugin->cls);
       *mhd_ret = TALER_MHD_REPLY_JSON_PACK (
         connection,
         MHD_HTTP_ACCEPTED,
@@ -313,7 +317,7 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
   struct WithdrawContext wc;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_varsize ("coin_ev",
-                              (void **) &wc.blinded_msg,
+                              &wc.blinded_msg,
                               &wc.blinded_msg_len),
     GNUNET_JSON_spec_fixed_auto ("reserve_sig",
                                  &wc.collectable.reserve_sig),
@@ -398,7 +402,6 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
         return TEH_RESPONSE_reply_expired_denom_pub_hash (
           rc->connection,
           &wc.collectable.denom_pub_hash,
-          GNUNET_TIME_timestamp_get (),
           TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
           "WITHDRAW");
       }
@@ -413,7 +416,6 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
       return TEH_RESPONSE_reply_expired_denom_pub_hash (
         rc->connection,
         &wc.collectable.denom_pub_hash,
-        GNUNET_TIME_timestamp_get (),
         TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
         "WITHDRAW");
     }
@@ -428,7 +430,6 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
         return TEH_RESPONSE_reply_expired_denom_pub_hash (
           rc->connection,
           &wc.collectable.denom_pub_hash,
-          GNUNET_TIME_timestamp_get (),
           TALER_EC_EXCHANGE_GENERIC_DENOMINATION_REVOKED,
           "WITHDRAW");
       }
@@ -437,22 +438,21 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
     }
   }
 
+  if (0 >
+      TALER_amount_add (&wc.collectable.amount_with_fee,
+                        &dk->meta.value,
+                        &dk->meta.fee_withdraw))
   {
-    if (0 >
-        TALER_amount_add (&wc.collectable.amount_with_fee,
-                          &dk->meta.value,
-                          &dk->meta.fee_withdraw))
-    {
-      GNUNET_JSON_parse_free (spec);
-      return TALER_MHD_reply_with_error (rc->connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_EXCHANGE_WITHDRAW_AMOUNT_FEE_OVERFLOW,
-                                         NULL);
-    }
-    TALER_amount_hton (&wc.wsrd.amount_with_fee,
-                       &wc.collectable.amount_with_fee);
+    GNUNET_JSON_parse_free (spec);
+    return TALER_MHD_reply_with_error (rc->connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_EXCHANGE_WITHDRAW_AMOUNT_FEE_OVERFLOW,
+                                       NULL);
   }
+  TALER_amount_hton (&wc.wsrd.amount_with_fee,
+                     &wc.collectable.amount_with_fee);
 
+  // FIXME: move this logic into libtalerutil!
   /* verify signature! */
   wc.wsrd.purpose.size
     = htonl (sizeof (wc.wsrd));
@@ -495,7 +495,7 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
                                     NULL);
   }
 
-  /* run transaction and sign (if not optimistically signed before) */
+  /* run transaction */
   {
     MHD_RESULT mhd_ret;