hot_standby_feedback is on, vacuum_defer_cleanup_age is not set, and
max_standby_{streaming,archive}_delay are set to -1.
>If all of these are off/zero then this sounds like the standby replays
>an exclusive lock which blocks a query running in the standby, then
>hits a vacuum record in the WAL log which it stops replay because the
>blocked query has an old enough snapshot to see the record being
>cleaned up.
Shouldn't the replay proceed once the query finishes (or is canceled),
though?