How does Rails handle large-scale multi-tenant data isolation with row-level security (RLS)?

Rails uses PostgreSQL row-level security to enforce tenant isolation at the database layer.

Row-Level Security (RLS) ensures that each query automatically filters rows based on tenant context. This moves security enforcement from application layer to database layer, reducing risk of accidental data leakage. Rails sets session variables or connection context to enforce tenant filtering rules. This is especially useful in high-security SaaS systems.