db-migrate

Applies SQL migrations from backend/db/migrations/ to the Postgres instance on container start, then exits.

Idempotency

Every migration uses CREATE TABLE IF NOT EXISTS and ON CONFLICT DO NOTHING patterns and is recorded in public.schema_migrations. The runner records each successful migration itself rather than relying on the SQL to do it. That closes a class of failure where a migration ran but its INSERT was missing, causing it to retry forever on next start.

Ordering

Services that depend on Postgres (oms, journal, user-service, replay-service) declare:

depends_on:
  db-migrate:
    condition: service_completed_successfully

so they wait for migrations to finish before starting. The migration container exits 0 on success and stays in Exited state, which is the healthy steady state, not an error.