#migrations

Upgrading PostgreSQL 16 to 18 with zero downtime: the whole runbook

A major version upgrade with a write pause you measure in seconds, instead of an outage you measure in hours. The plan, the preflight queries that catch what will bite you, building the new cluster from a standby with pg_createsubscriber, the sequence trap, schema changes during the window, the cutover script through PgBouncer, a rollback you can actually take, and what PostgreSQL 19 removes from this list.