diff --git a/include/wsrep/client_context.hpp b/include/wsrep/client_context.hpp
index 2b596ad..2887e12 100644
--- a/include/wsrep/client_context.hpp
+++ b/include/wsrep/client_context.hpp
@@ -190,6 +190,21 @@ namespace wsrep
          */
         int before_statement();
 
+        /*!
+         * Return values for after_statement() method.
+         */
+        enum after_statement_result
+        {
+            /*! Statement was executed succesfully */
+            asr_success,
+            /*! Statement execution encountered an error, the transaction
+             * was rolled back */
+            asr_error,
+            /*! Statement execution encountered an error, the transaction
+              was rolled back. However the statement was self contained
+              (e.g. autocommit statement) so it can be retried. */
+            asr_may_retry
+        };
         /*!
          * After statement execution operations.
          *
@@ -199,7 +214,7 @@ namespace wsrep
          * If overridden by the implementation, base class method
          * should be called after any implementation specific operations.
          */
-        void after_statement();
+        enum after_statement_result after_statement();
 
         int start_transaction()
         {
@@ -386,6 +401,7 @@ namespace wsrep
          */
         void state(wsrep::unique_lock<wsrep::mutex>& lock, enum state state);
 
+        virtual bool is_autocommit() const = 0;
         /*!
          * Virtual method to return true if the client operates
          * in two phase commit mode.
diff --git a/include/wsrep/client_service.hpp b/include/wsrep/client_service.hpp
new file mode 100644
index 0000000..c66b7d2
--- /dev/null
+++ b/include/wsrep/client_service.hpp
@@ -0,0 +1,137 @@
+//
+// Copyright (C) 2018 Codership Oy <info@codership.com>
+//
+
+/*! \file client_service.hpp
+ *
+ * This file will define a `callback` abstract interface for a
+ * DBMS client session service. The interface will define methods
+ * which will be called by the wsrep-lib under certain circumstances,
+ * for example when a transaction rollback is required by internal
+ * wsrep-lib operation or applier client needs to apply a write set.
+ *
+ * \todo Figure out better name for this interface.
+ */
+
+namespace wsrep
+{
+    class client_service
+    {
+    public:
+        virtual bool is_autocommit() const = 0;
+        /*!
+         * Return true if two pahase commit is required for transaction
+         * to commit.
+         */
+        virtual bool do_2pc() const = 0;
+
+        /*!
+         * Return true if the current transaction has been interrupted.
+         */
+        virtual bool interrupted() const = 0;
+
+        /*!
+         * Reset possible global or thread local parameters associated
+         * to the thread.
+         */
+        virtual void reset_globals() = 0;
+
+        /*!
+         * Store possible global or thread local parameters associated
+         * to the thread.
+         */
+        virtual void store_globals() = 0;
+
+        /*!
+         * Set up a data for replication.
+         */
+        virtual int prepare_data_for_replication(wsrep::data& data) = 0;
+
+
+        /*!
+         * Apply a write set.
+         */
+        virtual int apply() = 0;
+
+        /*!
+         * Prepare a transaction for commit.
+         */
+        virtual int prepare() = 0;
+
+        /*!
+         * Commit transaction.
+         */
+        virtual int commit() = 0;
+
+        /*!
+         * Roll back transaction.
+         */
+        virtual int rollback() = 0;
+
+        /*!
+         * Forcefully shut down the DBMS process or replication system.
+         * This may be called in situations where
+         * the process may encounter a situation where data integrity
+         * may not be guaranteed or other unrecoverable condition is
+         * encontered.
+         */
+        virtual void emergency_shutdown() = 0;
+
+        // Replaying
+        /*!
+         * Notify that the client will replay.
+         *
+         * \todo This should not be visible to DBMS level, should be
+         * handled internally by wsrep-lib.
+         */
+        virtual void will_replay() = 0;
+
+        /*!
+         * Replay the current transaction. The implementation must put
+         * the caller Client Context into applying mode and call
+         * client_context::replay().
+         *
+         * \todo This should not be visible to DBMS level, should be
+         * handled internally by wsrep-lib.
+         */
+        virtual int replay() = 0;
+
+        /*!
+         * Wait until all replaying transactions have been finished
+         * replaying.
+         *
+         * \todo This should not be visible to DBMS level, should be
+         * handled internally by wsrep-lib.
+         */
+        virtual void wait_for_replayers() = 0;
+
+        // Streaming replication
+        /*!
+         * Append a write set fragment into fragment storage.
+         */
+        virtual int append_fragment() = 0;
+    };
+
+    /*!
+     * Debug callback methods. These methods are called only in
+     * builds that have WITH_DEBUG defined.
+     */
+    class client_debug_callback
+    {
+    public:
+        /*!
+         * Enter debug sync point.
+         *
+         * @params sync_point Name of the debug sync point.
+         */
+        void debug_sync(const char* sync_point) = 0;
+
+        /*!
+         * Forcefully kill the process if the suicide_point has
+         * been enabled.
+         */
+        void debug_suicide(const char* suicide_point) = 0;
+    };
+
+
+}
diff --git a/src/client_context.cpp b/src/client_context.cpp
index 3ee1836..da6da91 100644
--- a/src/client_context.cpp
+++ b/src/client_context.cpp
@@ -105,14 +105,29 @@ int wsrep::client_context::before_statement()
     return 0;
 }
 
-void wsrep::client_context::after_statement()
+enum wsrep::client_context::after_statement_result
+wsrep::client_context::after_statement()
 {
+    // wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    assert(state() == s_exec);
 #if 0
     /*!
      * \todo Check for replay state, do rollback if requested.
      */
 #endif // 0
-    (void)transaction_.after_statement();
+    int ret(transaction_.after_statement());
+    if (ret)
+    {
+        if (is_autocommit())
+        {
+            return asr_may_retry;
+        }
+        else
+        {
+            return asr_error;
+        }
+    }
+    return asr_success;
 }
 
 // Private
diff --git a/src/dbms_simulator.cpp b/src/dbms_simulator.cpp
index f32c799..4668edf 100644
--- a/src/dbms_simulator.cpp
+++ b/src/dbms_simulator.cpp
@@ -336,6 +336,7 @@ public:
         return stats_;
     }
 private:
+    bool is_autocommit() const override { return false; }
     bool do_2pc() const override { return false; }
     int apply(const wsrep::data& data) override
     {
diff --git a/src/mock_client_context.hpp b/src/mock_client_context.hpp
index d6a5b61..bc4928a 100644
--- a/src/mock_client_context.hpp
+++ b/src/mock_client_context.hpp
@@ -22,6 +22,7 @@ namespace wsrep
               // Note: Mutex is initialized only after passed
               // to client_context constructor.
             , mutex_()
+            , is_autocommit_(false)
             , do_2pc_(do_2pc)
             , fail_next_applying_()
         { }
@@ -35,6 +36,7 @@ namespace wsrep
         int apply(const wsrep::data&);
         int commit();
         int rollback();
+        bool is_autocommit() const { return is_autocommit_; }
         bool do_2pc() const { return do_2pc_; }
         void will_replay(wsrep::transaction_context&) WSREP_OVERRIDE { }
         int replay(wsrep::transaction_context& tc) WSREP_OVERRIDE
@@ -61,6 +63,7 @@ namespace wsrep
         { fail_next_applying_ = fail_next_applying; }
     private:
         wsrep::default_mutex mutex_;
+        bool is_autocommit_;
         bool do_2pc_;
         bool fail_next_applying_;
     };