diff --git a/include/query_processor.h b/include/query_processor.h
index dd868f702..a288b10fe 100644
--- a/include/query_processor.h
+++ b/include/query_processor.h
@@ -384,7 +384,9 @@ class Query_Processor {
 	 * @return Old 'fast_routing_resultset' that has been replaced. Required to be freed by caller.
 	 */
 	SQLite3_result* load_fast_routing(const fast_routing_hashmap_t& fast_routing_hashmap);
-	int search_rules_fast_routing_dest_hg(khash_t(khStrInt)* _rules_fast_routing, const char* u, const char* s, int flagIN);
+	int search_rules_fast_routing_dest_hg(
+		khash_t(khStrInt)* _rules_fast_routing, const char* u, const char* s, int flagIN, bool lock
+	);
 	SQLite3_result * get_current_query_rules_fast_routing();
 	SQLite3_result * get_current_query_rules_fast_routing_inner();
 	int get_current_query_rules_fast_routing_count();
diff --git a/lib/ProxySQL_Admin.cpp b/lib/ProxySQL_Admin.cpp
index 528b4324a..a1ce30614 100644
--- a/lib/ProxySQL_Admin.cpp
+++ b/lib/ProxySQL_Admin.cpp
@@ -7536,8 +7536,8 @@ unsigned int ProxySQL_Admin::ProxySQL_Test___GenerateRandom_mysql_query_rules_fa
 	rc=admindb->prepare_v2(a, &statement1);
 	ASSERT_SQLITE_OK(rc, admindb);
 	admindb->execute("DELETE FROM mysql_query_rules_fast_routing");
-	char * username_buf = (char *)malloc(32);
-	char * schemaname_buf = (char *)malloc(64);
+	char * username_buf = (char *)malloc(128);
+	char * schemaname_buf = (char *)malloc(256);
 	//ui.username = username_buf;
 	//ui.schemaname = schemaname_buf;
 	if (empty==false) {
@@ -7548,7 +7548,7 @@ unsigned int ProxySQL_Admin::ProxySQL_Test___GenerateRandom_mysql_query_rules_fa
 	strcpy(schemaname_buf,"shard_name_");
 	int _k;
 	for (unsigned int i=0; i<cnt; i++) {
-		_k = fastrand()%20 + 1;
+		_k = fastrand()%117 + 1;
 		if (empty == false) {
 			for (int _i=0 ; _i<_k ; _i++) {
 				int b = fastrand()%10;
@@ -7556,7 +7556,7 @@ unsigned int ProxySQL_Admin::ProxySQL_Test___GenerateRandom_mysql_query_rules_fa
 			}
 			username_buf[10+_k]='\0';
 		}
-		_k = fastrand()%30 + 1;
+		_k = fastrand()%244+ 1;
 		for (int _i=0 ; _i<_k ; _i++) {
 			int b = fastrand()%10;
 			schemaname_buf[11+_i]='0' + b;
diff --git a/lib/Query_Processor.cpp b/lib/Query_Processor.cpp
index 96dd789f3..b41cad136 100644
--- a/lib/Query_Processor.cpp
+++ b/lib/Query_Processor.cpp
@@ -932,20 +932,26 @@ SQLite3_result * Query_Processor::get_current_query_rules_fast_routing() {
 }
 
 int Query_Processor::search_rules_fast_routing_dest_hg(
-	khash_t(khStrInt)* _rules_fast_routing, const char* u, const char* s, int flagIN
+	khash_t(khStrInt)* _rules_fast_routing, const char* u, const char* s, int flagIN, bool lock
 ) {
 	int dest_hg = -1;
+	const size_t u_len = strlen(u);
+	size_t keylen = u_len+strlen(rand_del)+strlen(s)+30; // 30 is a big number
+
 	char keybuf[256];
 	char * keybuf_ptr = keybuf;
-	size_t keylen = strlen(u)+strlen(rand_del)+strlen(s)+30; // 30 is a big number
-	if (keylen > 250) {
+
+	if (keylen >= sizeof(keybuf)) {
 		keybuf_ptr = (char *)malloc(keylen);
 	}
 	sprintf(keybuf_ptr,"%s%s%s---%d", u, rand_del, s, flagIN);
+
+	if (lock) {
+		pthread_rwlock_rdlock(&this->rwlock);
+	}
 	khiter_t k = kh_get(khStrInt, _rules_fast_routing, keybuf_ptr);
 	if (k == kh_end(_rules_fast_routing)) {
-		sprintf(keybuf_ptr,"%s%s---%d", rand_del, s, flagIN);
-		khiter_t k2 = kh_get(khStrInt, _rules_fast_routing, keybuf_ptr);
+		khiter_t k2 = kh_get(khStrInt, _rules_fast_routing, keybuf_ptr + u_len);
 		if (k2 == kh_end(_rules_fast_routing)) {
 		} else {
 			dest_hg = kh_val(_rules_fast_routing,k2);
@@ -953,7 +959,11 @@ int Query_Processor::search_rules_fast_routing_dest_hg(
 	} else {
 		dest_hg = kh_val(_rules_fast_routing,k);
 	}
-	if (keylen > 250) {
+	if (lock) {
+		pthread_rwlock_unlock(&this->rwlock);
+	}
+
+	if (keylen >= sizeof(keybuf)) {
 		free(keybuf_ptr);
 	}
 
@@ -2060,12 +2070,10 @@ __exit_process_mysql_query:
 
 		if (_thr_SQP_rules_fast_routing != nullptr) {
 			proxy_debug(PROXY_DEBUG_MYSQL_QUERY_PROCESSOR, 7, "Searching thread-local 'rules_fast_routing' hashmap with: user='%s', schema='%s', and flagIN='%d'\n", u, s, flagIN);
-			dst_hg = search_rules_fast_routing_dest_hg(_thr_SQP_rules_fast_routing, u, s, flagIN);
+			dst_hg = search_rules_fast_routing_dest_hg(_thr_SQP_rules_fast_routing, u, s, flagIN, false);
 		} else if (rules_fast_routing != nullptr) {
-			pthread_rwlock_rdlock(&this->rwlock);
 			proxy_debug(PROXY_DEBUG_MYSQL_QUERY_PROCESSOR, 7, "Searching global 'rules_fast_routing' hashmap with: user='%s', schema='%s', and flagIN='%d'\n", u, s, flagIN);
-			dst_hg = search_rules_fast_routing_dest_hg(rules_fast_routing, u, s, flagIN);
-			pthread_rwlock_unlock(&this->rwlock);
+			dst_hg = search_rules_fast_routing_dest_hg(rules_fast_routing, u, s, flagIN, true);
 		}
 
 		if (dst_hg != -1) {
@@ -3191,14 +3199,8 @@ int Query_Processor::testing___find_HG_in_mysql_query_rules_fast_routing_dual(
 	int ret = -1;
 	khash_t(khStrInt)* rules_fast_routing = _rules_fast_routing ? _rules_fast_routing : this->rules_fast_routing;
 
-	if (lock) {
-		pthread_rwlock_rdlock(&rwlock);
-	}
 	if (rules_fast_routing) {
-		ret = search_rules_fast_routing_dest_hg(rules_fast_routing, username, schemaname, flagIN);
-	}
-	if (lock) {
-		pthread_rwlock_unlock(&rwlock);
+		ret = search_rules_fast_routing_dest_hg(rules_fast_routing, username, schemaname, flagIN, lock);
 	}
 
 	return ret;