PostgreSQL

Use it for:

Owner records.
Password hashes.
Server-side sessions.
Tenants.
Logical Keys.
Public key components and versions.
Immutable policy versions.
Parent-child lineage.
One-time claim records.
Replay nonces.
Authored objects.
Alerts.
Append-only events.
Email outbox.

PostgreSQL Row-Level Security can restrict which tenant rows an application database role can select or modify, providing defense beyond application-level tenant filters.