Postgres

Set DATABASE_URL=postgres://... — that’s the entire migration from SQLite. The API, filter syntax, and rules are identical either way, verified by running the same integration test suite against both backends (crates/db/tests/). The one genuine capability upgrade: realtime becomes cross-node via LISTEN/NOTIFY, so a deployment behind a load balancer with more than one app instance stops silently dropping events for clients parked on a different instance than the one that handled a write. See Horizontal scaling for what that takes in practice: what’s stateless, the pg_notify mechanics, proxy config, migration races, and rolling deploys.