I have increasing replication lag on the hot standby. I grep processes on the stanby and see that WAL writer is in status "waiting". This always happens after (auto)vacuuming of table used by problem query. Once I kill problem query on the standby WAL segments are applied and the replication lag is no longer exists. Forgot to mention that max_standby_streaming_delay = 0 and max_standby_archive_delay = 0.
