and a few moments later...
TRUNCATE TABLE causes a table lock which stalls the cluster. DELETE FROM locks only the rows its deleting and doesn't block new rows from being inserted at the same time. I recommend removing all uses of truncate table to make Xenforo scale better in the future.
Also, SELECT ... FOR UPDATE causes a table lock leading to a cascading failure when a bunch of people try to vote on a poll. That should also be refactored to avoid that lock.