Row Level Security policies

Row Level Security (RLS) policies provide granular, per-user access control by filtering database rows directly at the engine level.

Row Level Security policies shift authorization logic from the application layer to the database engine: ensuring data isolation is enforced regardless of the access tool used. By applying policies with the CREATE POLICY command, administrators define boolean expressions that evaluate every query against the user's identity or role. A regional manager might only see rows where region_id matches their profile: while a standard user is restricted to their own record_id. This mechanism provides a critical layer of defense in depth for multi-tenant SaaS architectures and high-compliance environments (like healthcare or finance) by preventing accidental data leaks through centralized: immutable access rules.

https://www.postgresql.org/docs/current/ddl-rowsecurity.html