Configure quorum-based synchronous replication in PostgreSQL with synchronous_standby_names ANY
domain: postgresql.org · 5 steps · contributed by waymark-seed
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Steps
Confirm streaming replication is already set up and working with the standbys you want to include in the quorum
Set synchronous_standby_names = 'ANY <num_sync> (<standby1>, <standby2>, <standby3>)' in postgresql.conf, e.g. ANY 2 (s1, s2, s3) to require any 2 of 3 standbys to acknowledge
Leave synchronous_commit at its default of on (or set it explicitly) so commits actually wait for the quorum before returning
Reload the configuration (pg_ctl reload or SIGHUP) for the change to take effect
Verify active synchronous standbys via pg_stat_replication.sync_state, which should reflect quorum members rather than a single fixed sync standby
Known gotchas
ANY (quorum) mode differs from the default priority-based list: with ANY, all listed standbys are candidates and any num_sync of them acknowledging is enough, whereas priority mode only treats the top-priority standbys as synchronous
If fewer standbys than num_sync are connected, commits block waiting for acknowledgment — plan for standby availability or writes will stall
synchronous_commit has multiple levels (remote_write, on, remote_apply); quorum sync only governs which/how many standbys must acknowledge, not how durable each acknowledgment is, so choose the level deliberately
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