diff --git a/include/dba.php b/include/dba.php
index 1fff51f3d1..1f428bf465 100644
--- a/include/dba.php
+++ b/include/dba.php
@@ -816,7 +816,15 @@ class dba {
 	 * @return boolean was the lock successful?
 	 */
 	static public function lock($table) {
-		return self::e("LOCK TABLES `".self::$dbo->escape($table)."` WRITE");
+		// See here: https://dev.mysql.com/doc/refman/5.7/en/lock-tables-and-transactions.html
+		self::e("SET autocommit=0");
+		$success = self::e("LOCK TABLES `".self::$dbo->escape($table)."` WRITE");
+		if (!$success) {
+			self::e("SET autocommit=1");
+		} else {
+			self::$in_transaction = true;
+		}
+		return $success;
 	}
 
 	/**
@@ -825,7 +833,12 @@ class dba {
 	 * @return boolean was the unlock successful?
 	 */
 	static public function unlock() {
-		return self::e("UNLOCK TABLES");
+		// See here: https://dev.mysql.com/doc/refman/5.7/en/lock-tables-and-transactions.html
+		self::e("COMMIT");
+		$success = self::e("UNLOCK TABLES");
+		self::e("SET autocommit=1");
+		self::$in_transaction = false;
+		return $success;
 	}
 
 	/**
diff --git a/include/poller.php b/include/poller.php
index 3d53be0abb..1de9126d2d 100644
--- a/include/poller.php
+++ b/include/poller.php
@@ -573,7 +573,7 @@ function poller_worker_process() {
 	$highest_priority = 0;
 
 	if (poller_passing_slow($highest_priority)) {
-		dba::e('LOCK TABLES `workerqueue` WRITE');
+		dba::lock('workerqueue');
 
 		// Are there waiting processes with a higher priority than the currently highest?
 		$r = q("SELECT * FROM `workerqueue`
@@ -595,7 +595,7 @@ function poller_worker_process() {
 			return $r;
 		}
 	} else {
-		dba::e('LOCK TABLES `workerqueue` WRITE');
+		dba::lock('workerqueue');
 	}
 
 	// If there is no result (or we shouldn't pass lower processes) we check without priority limit
@@ -605,7 +605,7 @@ function poller_worker_process() {
 
 	// We only unlock the tables here, when we got no data
 	if (!dbm::is_result($r)) {
-		dba::e('UNLOCK TABLES');
+		dba::unlock();
 	}
 
 	return $r;
@@ -625,7 +625,7 @@ function poller_claim_process($queue) {
 
 	$success = dba::update('workerqueue', array('executed' => datetime_convert(), 'pid' => $mypid),
 			array('id' => $queue["id"], 'pid' => 0));
-	dba::e('UNLOCK TABLES');
+	dba::unlock();
 
 	if (!$success) {
 		logger("Couldn't update queue entry ".$queue["id"]." - skip this execution", LOGGER_DEBUG);
diff --git a/include/socgraph.php b/include/socgraph.php
index fbac08cc97..7a39e388be 100644
--- a/include/socgraph.php
+++ b/include/socgraph.php
@@ -1995,10 +1995,11 @@ function get_gcontact_id($contact) {
 	if (in_array($contact["network"], array(NETWORK_DFRN, NETWORK_DIASPORA, NETWORK_OSTATUS)))
 		$contact["url"] = clean_contact_url($contact["url"]);
 
-	$r = q("SELECT `id`, `last_contact`, `last_failure`, `network` FROM `gcontact` WHERE `nurl` = '%s' LIMIT 2",
+	dba::lock('gcontact');
+	$r = q("SELECT `id`, `last_contact`, `last_failure`, `network` FROM `gcontact` WHERE `nurl` = '%s' LIMIT 1",
 		dbesc(normalise_link($contact["url"])));
 
-	if ($r) {
+	if (dbm::is_result($r)) {
 		$gcontact_id = $r[0]["id"];
 
 		// Update every 90 days
@@ -2036,17 +2037,13 @@ function get_gcontact_id($contact) {
 			$doprobing = in_array($r[0]["network"], array(NETWORK_DFRN, NETWORK_DIASPORA, NETWORK_OSTATUS, ""));
 		}
 	}
+	dba::unlock();
 
 	if ($doprobing) {
 		logger("Last Contact: ". $last_contact_str." - Last Failure: ".$last_failure_str." - Checking: ".$contact["url"], LOGGER_DEBUG);
 		proc_run(PRIORITY_LOW, 'include/gprobe.php', bin2hex($contact["url"]));
 	}
 
-	if ((dbm::is_result($r)) AND (count($r) > 1) AND ($gcontact_id > 0) AND ($contact["url"] != ""))
-	 q("DELETE FROM `gcontact` WHERE `nurl` = '%s' AND `id` != %d",
-		dbesc(normalise_link($contact["url"])),
-		intval($gcontact_id));
-
 	return $gcontact_id;
 }
 
diff --git a/src/Util/Lock.php b/src/Util/Lock.php
index e8011bf59f..7cc3472e69 100644
--- a/src/Util/Lock.php
+++ b/src/Util/Lock.php
@@ -57,7 +57,7 @@ class Lock {
 
 		$memcache = self::memcache();
 		if (is_object($memcache)) {
-			$wait_sec = 1;
+			$wait_sec = 0.2;
 			$cachekey = get_app()->get_hostname().";lock:".$fn_name;
 
 			do {
@@ -77,9 +77,9 @@ class Lock {
 					$got_lock = true;
 				}
 				if (!$got_lock) {
-					sleep($wait_sec);
+					usleep($wait_sec * 1000000);
 				}
-			} while (!$got_lock AND ((time() - $start) < $timeout));
+			} while (!$got_lock AND ((time(true) - $start) < $timeout));
 
 			return $got_lock;
 		}