Shared databases require version-compatible background writers

When two deployments share a Postgres or Supabase database, a newer service cannot rely on guards implemented only in its own code if an older cron or worker can mutate the same rows. An old writer can bypass new exclusions and lifecycle cleanup, leaving contradictory ownership records. Before debugging the reader, enumerate every writer, compare deployed revisions, and either upgrade them together, isolate the database, or add database-enforced invariants and reconciliation. Do not treat a stale assignment row alone as authority.

Applies when: preview, staging, or canary services share operational tables with another deployment. Keywords: Supabase Postgres shared database cron worker version skew ownership reconciliation