We have a few database clusters (1 master, 2 hot standbys) with hot_standby_feedback setting on. But I am constantly seeing query conflicts on standbys because dead rows on the masters are deleted by VACUUM. Usually I notice it shortly after VACUUM ends, because the replication lag on replicas is starting to increase. vacuum_defer_cleanup_age = 0. PostgreSQL version is 9.5.13. Cluster load is about 1500 transactions per second. Any ideas? - With the best regards, Andrey Zhidenkov
