Question

Every deploy runs migrations as a gated pre-step. Today's 15:00 deploy hangs in the migration step: the migration is a quick `ADD COLUMN ... DEFAULT now()` that should take a second, but the deploy pipeline is stuck and times out after 10 minutes, blocking the release of an urgent hotfix. Dashboards: the app is otherwise healthy (the migration's ALTER hasn't acquired its lock so it isn't blocking live queries yet — it's waiting), `pg_stat_activity` shows the ALTER in `lock not available`/waiting, and the migration tool is configured with a `lock_timeout` of 0 (infinite) so it just waits. Ahead of it in the lock queue: a long-running analytics transaction that's been open for 40 minutes. New queries are starting to queue behind the ALTER. Triage and mitigate.