Slowness reported in https://github.com/addshore/mediawiki-docker-dev/issues/57 and oncce investigated this ticket was created for searchability on phabricator.
LBFactory, $this->memStash = $conf['memStash'] ?? new EmptyBagOStuff();
If you have a master slave setup using $wgDBServers and no fancy load balancer config memStash is an EmptyBagOStuff
which causes the ChronologyProtector to get stuck in a wait loop waiting for a cache key in an EmptyBagOStuff
I guess something should behave slightly differently in there, perhaps this should be using CACHE_ANYTHING as a fallback instead of an empty bag