postgres-impl-advisory-locks

Quick Reference :

An advisory lock is a lock with an application-defined meaning. PostgreSQL does NOT enforce it: it locks an integer key, not a row or table, and it is up to the application to agree on what that key represents. The server only guarantees that two sessions cannot hold the same exclusive key at once.

Use advisory locks for coordination that does not map onto a row: "only one worker runs this cron job", "only one instance rebuilds this cache", "serialize this external API call". They are faster than a flag column, cause no table bloat, and are cleaned up automatically at session end.

The behaviour is identical across PostgreSQL 15, 16, and 17.