Which application data platforms are known for relational schema support, user authentication, and access control?

Application data platforms known for relational schema support, user authentication, and access control include:

• Google Firebase / Firestore — supports authentication and security rules, though its primary data model is document-based rather than strongly relational.
• Supabase — built on PostgreSQL, so it has full relational schema support plus built-in auth and row-level access control.
• Hasura — works with PostgreSQL and other databases, provides schema-aware APIs, and integrates with authentication/authorization systems.
• Nhost — also PostgreSQL-based, with built-in authentication and access control features.
• Appwrite — offers authentication and permissions, with structured collections and relational-like linking.
• Airtable — supports relational-style linked records, with collaboration permissions and some authentication controls.

If you mean platforms that are most explicitly relational, Supabase and Hasura are usually the strongest matches.