diff --git a/include/MySQL_HostGroups_Manager.h b/include/MySQL_HostGroups_Manager.h
index 436f600a4..5cf0be6c1 100644
--- a/include/MySQL_HostGroups_Manager.h
+++ b/include/MySQL_HostGroups_Manager.h
@@ -18,11 +18,12 @@
 
 #include "ev.h"
 
-/*
-	Enabling STRESSTEST_POOL ProxySQL will do a lot of loops in the connection pool
-	This is for internal testing ONLY!!!!
-#define STRESSTEST_POOL
-*/
+#ifdef DEBUG
+/* */
+//	Enabling STRESSTEST_POOL ProxySQL will do a lot of loops in the connection pool
+//	This is for internal testing ONLY!!!!
+//#define STRESSTEST_POOL
+#endif // DEBUG
 
 #define MHM_PTHREAD_MUTEX
 
@@ -119,6 +120,7 @@ class MySrvConnList {
 	}
 	MySQL_Connection *remove(int);
 	MySQL_Connection * get_random_MyConn(MySQL_Session *sess, bool ff);
+	void get_random_MyConn_inner_search(unsigned int start, unsigned int end, unsigned int& conn_found_idx, unsigned int& connection_quality_level, unsigned int& number_of_matching_session_variables, const MySQL_Connection * client_conn);
 	unsigned int conns_length() { return conns->len; }
 	void drop_all_connections();
 	MySQL_Connection *index(unsigned int);
diff --git a/include/mysql_connection.h b/include/mysql_connection.h
index b60abfe61..a60a945cb 100644
--- a/include/mysql_connection.h
+++ b/include/mysql_connection.h
@@ -215,7 +215,9 @@ class MySQL_Connection {
 	bool get_gtid(char *buff, uint64_t *trx_id);
 	void reduce_auto_increment_delay_token() { if (auto_increment_delay_token) auto_increment_delay_token--; };
 
-	bool match_tracked_options(MySQL_Connection *c);
+	bool match_tracked_options(const MySQL_Connection *c);
+	bool requires_CHANGE_USER(const MySQL_Connection *client_conn);
+	unsigned int number_of_matching_session_variables(const MySQL_Connection *client_conn, unsigned int& not_matching);
 	unsigned long get_mysql_thread_id() { return mysql ? mysql->thread_id : 0; }
 };
 #endif /* __CLASS_MYSQL_CONNECTION_H */
diff --git a/lib/MySQL_HostGroups_Manager.cpp b/lib/MySQL_HostGroups_Manager.cpp
index 02979a285..7d386dba3 100644
--- a/lib/MySQL_HostGroups_Manager.cpp
+++ b/lib/MySQL_HostGroups_Manager.cpp
@@ -2986,11 +2986,67 @@ MySrvC *MyHGC::get_random_MySrvC(char * gtid_uuid, uint64_t gtid_trxid, int max_
 
 //MySrvC * MySrvList::idx(unsigned int i) { return (MySrvC *)servers->index(i); }
 
+void MySrvConnList::get_random_MyConn_inner_search(unsigned int start, unsigned int end, unsigned int& conn_found_idx, unsigned int& connection_quality_level, unsigned int& number_of_matching_session_variables, const MySQL_Connection * client_conn) {
+	char *schema = client_conn->userinfo->schemaname;
+	MySQL_Connection * conn=NULL;
+	unsigned int k;
+	for (k = start;  k < end; k++) {
+		conn = (MySQL_Connection *)conns->index(k);
+		if (conn->match_tracked_options(client_conn)) {
+			if (connection_quality_level == 0) {
+				// this is our best candidate so far
+				connection_quality_level = 1;
+				conn_found_idx = k;
+			}
+			if (conn->requires_CHANGE_USER(client_conn)==false) {
+				if (connection_quality_level == 1) {
+					// this is our best candidate so far
+					connection_quality_level = 2;
+					conn_found_idx = k;
+				}
+				unsigned int cnt_match = 0; // number of matching session variables
+				unsigned int not_match = 0; // number of not matching session variables
+				cnt_match = conn->number_of_matching_session_variables(client_conn, not_match);
+				if (strcmp(conn->userinfo->schemaname,schema)==0) {
+					cnt_match++;
+				} else {
+					not_match++;
+				}
+				if (not_match==0) {
+					// it seems we found the perfect connection
+					number_of_matching_session_variables = cnt_match;
+					connection_quality_level = 3;
+					conn_found_idx = k;
+					return; // exit immediately, we found the perfect connection
+				} else {
+					// we didn't find the perfect connection
+					// but maybe is better than what we have so far?
+					if (cnt_match > number_of_matching_session_variables) {
+						// this is our best candidate so far
+						number_of_matching_session_variables = cnt_match;
+						conn_found_idx = k;
+					}
+				}
+			}
+		}
+	}
+}
+
+
+
 MySQL_Connection * MySrvConnList::get_random_MyConn(MySQL_Session *sess, bool ff) {
 	MySQL_Connection * conn=NULL;
 	unsigned int i;
+	unsigned int conn_found_idx;
 	unsigned int l=conns_length();
+	unsigned int connection_quality_level = 0;
 	bool needs_warming = false;
+	// connection_quality_level:
+	// 0 : not found any good connection, tracked options are not OK
+	// 1 : tracked options are OK , but CHANGE USER is required
+	// 2 : tracked options are OK , CHANGE USER is not required, but some SET statement or INIT_DB needs to be executed
+	// 3 : tracked options are OK , CHANGE USER is not required, and it seems that SET statements or INIT_DB ARE not required
+	unsigned int number_of_matching_session_variables = 0; // this includes session variables AND schema
 	if (mysql_thread___connection_warming) {
 		unsigned int total_connections = mysrvc->ConnectionsFree->conns_length()+mysrvc->ConnectionsUsed->conns_length();
 		unsigned int expected_warm_connections = mysql_thread___free_connections_pct*mysrvc->max_connections/100;
@@ -3005,50 +3061,25 @@ MySQL_Connection * MySrvConnList::get_random_MyConn(MySQL_Session *sess, bool ff
 			i=fastrand()%l;
 		}
 		if (sess && sess->client_myds && sess->client_myds->myconn && sess->client_myds->myconn->userinfo) {
-			// try to match schemaname AND username
-			char *schema = sess->client_myds->myconn->userinfo->schemaname;
-			char *username = sess->client_myds->myconn->userinfo->username;
 			MySQL_Connection * client_conn = sess->client_myds->myconn;
-			bool conn_found = false;
-			unsigned int k;
-			bool options_matching_found = false;
-			for (k = i; conn_found == false && k < l; k++) {
-				conn = (MySQL_Connection *)conns->index(k);
-				if (conn->match_tracked_options(client_conn)) {
-					if (options_matching_found == false) {
-						options_matching_found = true;
-					}
-					if (strcmp(conn->userinfo->schemaname,schema)==0 && strcmp(conn->userinfo->username,username)==0) {
-						conn_found = true;
-						i = k;
-					}
-				}
-			}
-			if (conn_found == false ) {
-				for (k = 0; conn_found == false && k < i; k++) {
-					conn = (MySQL_Connection *)conns->index(k);
-					if (conn->match_tracked_options(client_conn)) {
-						if (options_matching_found == false) {
-							options_matching_found = true;
-						}
-						if (strcmp(conn->userinfo->schemaname,schema)==0 && strcmp(conn->userinfo->username,username)==0) {
-							conn_found = true;
-							i = k;
-						}
-					}
-				}
+			get_random_MyConn_inner_search(i, l, conn_found_idx, connection_quality_level, number_of_matching_session_variables, client_conn);
+			if (connection_quality_level !=3 ) { // we didn't find the perfect connection
+				get_random_MyConn_inner_search(0, i, conn_found_idx, connection_quality_level, number_of_matching_session_variables, client_conn);
 			}
-			if (conn_found == true) {
-				conn=(MySQL_Connection *)conns->remove_index_fast(i);
-			} else {
-				if (options_matching_found == false) {
+			// connection_quality_level:
+			// 1 : tracked options are OK , but CHANGE USER is required
+			// 2 : tracked options are OK , CHANGE USER is not required, but some SET statement or INIT_DB needs to be executed
+			switch (connection_quality_level) {
+				case 0: // not found any good connection, tracked options are not OK
 					// we must create a new connection
 					conn = new MySQL_Connection();
 					conn->parent=mysrvc;
 					__sync_fetch_and_add(&MyHGM->status.server_connections_created, 1);
 					proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Returning MySQL Connection %p, server %s:%d\n", conn, conn->parent->address, conn->parent->port);
-				} else {
+					break;
+				case 1: //tracked options are OK , but CHANGE USER is required
 					// we may consider creating a new connection
+					{
 					unsigned int conns_free = mysrvc->ConnectionsFree->conns_length();
 					unsigned int conns_used = mysrvc->ConnectionsUsed->conns_length();
 					if ((conns_used > conns_free) && (mysrvc->max_connections > (conns_free/2 + conns_used/2)) ) {
@@ -3057,9 +3088,18 @@ MySQL_Connection * MySrvConnList::get_random_MyConn(MySQL_Session *sess, bool ff
 						__sync_fetch_and_add(&MyHGM->status.server_connections_created, 1);
 						proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Returning MySQL Connection %p, server %s:%d\n", conn, conn->parent->address, conn->parent->port);
 					} else {
-						conn=(MySQL_Connection *)conns->remove_index_fast(i);
+						conn=(MySQL_Connection *)conns->remove_index_fast(conn_found_idx);
 					}
-				}
+					}
+					break;
+				case 2: // tracked options are OK , CHANGE USER is not required, but some SET statement or INIT_DB needs to be executed
+				case 3: // tracked options are OK , CHANGE USER is not required, and it seems that SET statements or INIT_DB ARE not required
+					// here we return the best connection we have, no matter if connection_quality_level is 2 or 3
+					conn=(MySQL_Connection *)conns->remove_index_fast(conn_found_idx);
+					break;
+				default: // this should never happen
+					assert(0);
+					break;
 			}
 		} else {
 			conn=(MySQL_Connection *)conns->remove_index_fast(i);
diff --git a/lib/MySQL_Session.cpp b/lib/MySQL_Session.cpp
index 9ee9d896f..0bb497212 100644
--- a/lib/MySQL_Session.cpp
+++ b/lib/MySQL_Session.cpp
@@ -1894,6 +1894,25 @@ bool MySQL_Session::handler_again___verify_backend_user_schema() {
 			NEXT_IMMEDIATE_NEW(CHANGING_SCHEMA);
 		}
 	}
+	// if we reach here, the username is the same
+	if (myds->myconn->requires_CHANGE_USER(client_myds->myconn)) {
+		// if we reach here, even if the username is the same,
+		// the backend connection has some session variable set
+		// that the client never asked for
+		// because we can't unset variables, we will reset the connection
+		switch(status) {
+			case PROCESSING_QUERY:
+			case PROCESSING_STMT_PREPARE:
+			case PROCESSING_STMT_EXECUTE:
+				previous_status.push(status);
+				break;
+			default:
+				assert(0);
+				break;
+		}
+		mybe->server_myds->wait_until = thread->curtime + mysql_thread___connect_timeout_server*1000;   // max_timeout
+		NEXT_IMMEDIATE_NEW(CHANGING_USER_SERVER);
+	}
 	return false;
 }
 
@@ -5837,20 +5856,58 @@ void MySQL_Session::handler___client_DSS_QUERY_SENT___server_DSS_NOT_INITIALIZED
 					}
 				}
 				uuid[n]='\0';
+#ifndef STRESSTEST_POOL
 				mc=thread->get_MyConn_local(mybe->hostgroup_id, this, uuid, trxid, -1);
+#endif // STRESSTEST_POOL
 			} else {
+#ifndef STRESSTEST_POOL
 				mc=thread->get_MyConn_local(mybe->hostgroup_id, this, NULL, 0, (int)qpo->max_lag_ms);
+#endif // STRESSTEST_POOL
 			}
 		}
+#ifdef STRESSTEST_POOL
+		// Check STRESSTEST_POOL in MySQL_HostGroups_Manager.h
+		// Note: this works only if session_fast_forward==false and create_new_conn is false too
+#define NUM_SLOW_LOOPS 1000
+		// if STRESSTESTPOOL_MEASURE is define, time is measured in Query_Processor_time_nsec
+		// even if not the right variable
+//#define STRESSTESTPOOL_MEASURE
+#ifdef STRESSTESTPOOL_MEASURE
+		timespec begint;
+		timespec endt;
+		clock_gettime(CLOCK_MONOTONIC,&begint);
+#endif // STRESSTESTPOOL_MEASURE
+		for (unsigned int loops=0; loops < NUM_SLOW_LOOPS; loops++) {
+#endif // STRESSTEST_POOL
+
 		if (mc==NULL) {
 			if (trxid) {
 				mc=MyHGM->get_MyConn_from_pool(mybe->hostgroup_id, this, (session_fast_forward || qpo->create_new_conn), uuid, trxid, -1);
 			} else {
 				mc=MyHGM->get_MyConn_from_pool(mybe->hostgroup_id, this, (session_fast_forward || qpo->create_new_conn), NULL, 0, (int)qpo->max_lag_ms);
 			}
+#ifdef STRESSTEST_POOL
+			if (mc && (loops < NUM_SLOW_LOOPS - 1)) {
+				if (mc->mysql) {
+					mybe->server_myds->attach_connection(mc);
+					mybe->server_myds->DSS=STATE_NOT_INITIALIZED;
+					mybe->server_myds->return_MySQL_Connection_To_Pool();
+					mc=NULL;
+				}
+			}
+#endif // STRESSTEST_POOL
 		} else {
 			thread->status_variables.stvar[st_var_ConnPool_get_conn_immediate]++;
 		}
+#ifdef STRESSTEST_POOL
+#ifdef STRESSTESTPOOL_MEASURE
+		clock_gettime(CLOCK_MONOTONIC,&endt);
+		thread->status_variables.query_processor_time=thread->status_variables.query_processor_time +
+			(endt.tv_sec*1000000000+endt.tv_nsec) -
+			(begint.tv_sec*1000000000+begint.tv_nsec);
+#endif // STRESSTESTPOOL_MEASURE
+		}
+#endif // STRESSTEST_POOL
 		if (mc) {
 			mybe->server_myds->attach_connection(mc);
 			thread->status_variables.stvar[st_var_ConnPool_get_conn_success]++;
diff --git a/lib/MySQL_Thread.cpp b/lib/MySQL_Thread.cpp
index 6a8fb9c28..54504f353 100644
--- a/lib/MySQL_Thread.cpp
+++ b/lib/MySQL_Thread.cpp
@@ -6108,97 +6108,58 @@ void MySQL_Thread::Get_Memory_Stats() {
 
 
 MySQL_Connection * MySQL_Thread::get_MyConn_local(unsigned int _hid, MySQL_Session *sess, char *gtid_uuid, uint64_t gtid_trxid, int max_lag_ms) {
+	// some sanity check
+	if (sess == NULL) return NULL;
+	if (sess->client_myds == NULL) return NULL;
+	if (sess->client_myds->myconn == NULL) return NULL;
+	if (sess->client_myds->myconn->userinfo == NULL) return NULL;
 	unsigned int i;
-	unsigned int bc = 0; // best candidate
-	bool pcf = false; // possible candidate found
-	unsigned int npc = 0; // number of possible candidates
-	std::vector<MySrvC *> parents;
+	std::vector<MySrvC *> parents; // this is a vector of srvers that needs to be excluded in case gtid_uuid is used
 	MySQL_Connection *c=NULL;
-//	MySQL_Connection *_candidate = NULL; // this will be used when we will pass optional parameters
 	for (i=0; i<cached_connections->len; i++) {
 		c=(MySQL_Connection *)cached_connections->index(i);
-		if (c->parent->myhgc->hid==_hid && sess->client_myds->myconn->match_tracked_options(c)) {
-
-			if (gtid_uuid) {
-				// we first check if we already excluded this parent (MySQL Server)
-				MySrvC *mysrvc = c->parent;
-				std::vector<MySrvC *>::iterator it;
-				it = find(parents.begin(), parents.end(), mysrvc);
-				if (it != parents.end()) {
-					// we didn't exclude this server (yet?)
-					bool gtid_found = false;
-					gtid_found = MyHGM->gtid_exists(mysrvc, gtid_uuid, gtid_trxid);
-					if (gtid_found) {
-						//c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
-						//return c;
-
-						if (pcf == false) {
-							bc = i;
-							pcf = true;
-						}
-						//npc++;
-						if (sess && sess->client_myds && sess->client_myds->myconn && sess->client_myds->myconn->userinfo) {
-							char *schema = sess->client_myds->myconn->userinfo->schemaname;
-							char *username = sess->client_myds->myconn->userinfo->username;
-							if (strcmp(c->userinfo->schemaname,schema)==0 && strcmp(c->userinfo->username,username)==0) {
+		if (c->parent->myhgc->hid==_hid && sess->client_myds->myconn->match_tracked_options(c)) { // options are all identical
+			if (
+				(gtid_uuid == NULL) || // gtid_uuid is not used
+				(gtid_uuid && find(parents.begin(), parents.end(), c->parent) == parents.end()) // the server is currently not excluded
+			) {
+				MySQL_Connection *client_conn = sess->client_myds->myconn;
+				if (c->requires_CHANGE_USER(client_conn)==false) { // CHANGE_USER is not required
+					char *schema = client_conn->userinfo->schemaname;
+					if (strcmp(c->userinfo->schemaname,schema)==0) { // same schema
+						unsigned int not_match = 0; // number of not matching session variables
+						c->number_of_matching_session_variables(client_conn, not_match);
+						if (not_match == 0) { // all session variables match
+							if (gtid_uuid) { // gtid_uuid is used
+								// we first check if we already excluded this parent (MySQL Server)
+								MySrvC *mysrvc = c->parent;
+								std::vector<MySrvC *>::iterator it;
+								it = find(parents.begin(), parents.end(), mysrvc);
+								if (it != parents.end()) {
+									// we didn't exclude this server (yet?)
+									bool gtid_found = false;
+									gtid_found = MyHGM->gtid_exists(mysrvc, gtid_uuid, gtid_trxid);
+									if (gtid_found) { // this server has the correct GTID
+										c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
+										return c;
+									} else {
+										parents.push_back(mysrvc); // stop evaluating this server
+									}
+								}
+							} else { // gtid_is not used
+								if (max_lag_ms >= 0) {
+									if ((unsigned int)max_lag_ms < (c->parent->aws_aurora_current_lag_us / 1000)) {
+										status_variables.stvar[st_var_aws_aurora_replicas_skipped_during_query]++;
+										continue;
+									}
+								}
+								// return the connection
 								c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
 								return c;
 							}
-						} else {
-							c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
-							return c;
 						}
-
-
-
-					} else {
-						parents.push_back(mysrvc); // stop evaluating this server
-//						if (_candidate == NULL) {
-//							_candidate = c; // this server is a potential candidate
-//						}
-					}
-				}
-			} else {
-//				c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
-
-				if (max_lag_ms >= 0) {
-					if ((unsigned int)max_lag_ms < (c->parent->aws_aurora_current_lag_us / 1000)) {
-						status_variables.stvar[st_var_aws_aurora_replicas_skipped_during_query]++;
-						continue;
 					}
 				}
-				if (pcf == false) {
-					bc = i;
-					pcf = true;
-				}
-				npc++;
-				if (sess && sess->client_myds && sess->client_myds->myconn && sess->client_myds->myconn->userinfo) {
-					char *schema = sess->client_myds->myconn->userinfo->schemaname;
-					char *username = sess->client_myds->myconn->userinfo->username;
-					if (strcmp(c->userinfo->schemaname,schema)==0 && strcmp(c->userinfo->username,username)==0) {
-						c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
-						return c;
-					}
-				} else {
-					c=(MySQL_Connection *)cached_connections->remove_index_fast(i);
-					return c;
-				}
-
-				//return c;
-			}
-		}
-	}
-//	if (_candidate) {
-//		return _candidate;
-//	}
-	if (pcf) { // there was a possible connection, but we skipped trying to find a better one
-		if (gtid_uuid) {
-			c=(MySQL_Connection *)cached_connections->remove_index_fast(bc);
-			return c;
-		} else {
-			if (npc > 5) { // more candidates were evaluated
-				c=(MySQL_Connection *)cached_connections->remove_index_fast(bc);
-				return c;
 			}
 		}
 	}
diff --git a/lib/mysql_connection.cpp b/lib/mysql_connection.cpp
index 01e6c9f4b..fcbc5d4b4 100644
--- a/lib/mysql_connection.cpp
+++ b/lib/mysql_connection.cpp
@@ -480,7 +480,43 @@ bool MySQL_Connection::get_status_sql_log_bin0() {
 	return status_flags & STATUS_MYSQL_CONNECTION_SQL_LOG_BIN0;
 }
 
-bool MySQL_Connection::match_tracked_options(MySQL_Connection *c) {
+bool MySQL_Connection::requires_CHANGE_USER(const MySQL_Connection *client_conn) {
+	char *username = client_conn->userinfo->username;
+	if (strcmp(userinfo->username,username)) {
+		// the two connections use different usernames
+		// The connection need to be reset with CHANGE_USER
+		return true;
+	}
+	for (auto i = 0; i < SQL_NAME_LAST; i++) {
+		if (client_conn->var_hash[i] == 0) {
+			if (var_hash[i]) {
+				// this connection has a variable set that the
+				// client connection doesn't have.
+				// Since connection cannot be unset , this connection
+				// needs to be reset with CHANGE_USER
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
+unsigned int MySQL_Connection::number_of_matching_session_variables(const MySQL_Connection *client_conn, unsigned int& not_matching) {
+	unsigned int ret=0;
+	for (auto i = 0; i < SQL_NAME_LAST; i++) {
+		if (client_conn->var_hash[i] && i != SQL_CHARACTER_ACTION) { // client has a variable set
+			if (var_hash[i] == client_conn->var_hash[i]) { // server conection has the variable set to the same value
+				ret++;
+			} else {
+				not_matching++;
+			}
+		}
+	}
+	return ret;
+}
+
+
+bool MySQL_Connection::match_tracked_options(const MySQL_Connection *c) {
 	uint32_t cf1 = options.client_flag; // own client flags
 	uint32_t cf2 = c->options.client_flag; // other client flags
 	if ((cf1 & CLIENT_FOUND_ROWS) == (cf2 & CLIENT_FOUND_ROWS)) {
@@ -532,6 +568,7 @@ void MySQL_Connection::connect_start() {
 		std::stringstream ss;
 		ss << c->nr;
 
+		mysql_variables.server_set_value(myds->sess, SQL_CHARACTER_SET, ss.str().c_str());
 		mysql_variables.server_set_value(myds->sess, SQL_CHARACTER_SET_RESULTS, ss.str().c_str());
 		mysql_variables.server_set_value(myds->sess, SQL_CHARACTER_SET_CLIENT, ss.str().c_str());
 		mysql_variables.server_set_value(myds->sess, SQL_CHARACTER_SET_CONNECTION, ss.str().c_str());