Directus

Directus is a layer that sits on top of an existing SQL database rather than replacing it. Point it at a database and it introspects the schema, then generates a REST and GraphQL API plus an admin application for the tables it finds. The database remains the source of truth. That inversion is the main difference from a conventional CMS. Content is not locked in an application-specific structure: the tables are ordinary SQL tables, readable by other tools and migrations. Custom fields, relations, and permissions are configured in Directus and stored in the same database, so a DBA can still work with the schema directly. The product is open source and self-hostable, with a paid cloud offering. It fits teams that already have a database and want an admin interface and API over it without migrating. It is a weaker fit when the schema is expected to change constantly, since the database is the contract.