protected function loadFromDB( $code, $mode = null ) {
global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
- $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA );
+ // (T164666) The query here performs really poorly on WMF's
+ // contributions replicas. We don't have a way to say "any group except
+ // contributions", so for the moment let's specify 'api'.
+ // @todo: Get rid of this hack.
+ $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
$cache = [];