PostgreSQL 17 introduces failover slots that enhance high-availability setups. A replication slot ensures that data remains reliable and consistent between nodes during replication, whereas a failover slot ensures consistency between nodes, specifically during and after a failover.

Failover slots are a powerful feature that ensures logical replication can continue seamlessly, even after a failover to a standby server. Using failover slots allows logical replication slots to be automatically synchronized across primary and standby nodes, significantly reducing downtime and the need for manual intervention during a failover.

https://dzone.com/articles/setting-up-failover-slots-in-postgresql-17