starlette-jsonapi does not come with a data layer implementation, so you should be able to pick any available ORM (sync or async). This also means that you are going to get a simple interface for writing JSON:API compliant resources, with some helpers to make it easier.
Data access is on you, the default implementation will otherwise return 405 errors.
100% tests coverage
basic JSON:API serialization and deserialization
starlette friendly route generation
exception handlers to serialize as JSON:API errors
support for client generated IDs
support top level meta objects
OpenAPI 3.x (f.k.a Swagger) integration