How does Rails handle large-scale multi-layer authentication and authorization architecture?

Rails implements layered security using authentication (identity), authorization (permissions), and policy enforcement layers.

Authentication verifies identity using sessions, JWT, or OAuth2. Authorization defines what an authenticated user can access using role-based or attribute-based models. Rails often uses Devise for authentication and Pundit or Policy objects for authorization. At scale, external IAM systems centralize identity management while Rails enforces fine-grained access rules at the application layer.