Failover slot
Also called: failover-enabled slot
A failover slot is a logical replication slot marked (with failover = true) to survive a failover. PostgreSQL 17 mirrors such slots onto a standby, so when that standby is promoted the logical subscribers' bookmark already exists on the new primary at a safe position.
What this means
A logical replication slot, the bookmark that remembers how far a subscriber has read, marked to survive a failover. Postgres 17 copies such a slot onto a standby, so when that standby is promoted the subscribers' bookmark already exists on the new primary and they don't lose their place.
Why it matters operationally
Before this, promoting a standby destroyed all logical slots, forcing subscribers and CDC pipelines to be re-seeded with the risk of gaps or duplicates. Marking a slot for failover makes logical replication survive a role change cleanly.