Normally the database and message queue is decoupled from the backend service. This decoupling makes managing simpler and make cross-language things easier.
But if the type system need to cover all these components, then they start coupling again.
Coupling is not necessarily a bad thing as long as it gives good developer UX. If the database is tightly coupled with programming language, then it looks like ORM but better. And it probably can also reduce CRUD biolerplate or N+1 issue etc.
Related, there is SpacetimeDB that make backend run within database, and the backend code is highly coupled with SpacetimeDB's own API
But if the type system need to cover all these components, then they start coupling again.
Coupling is not necessarily a bad thing as long as it gives good developer UX. If the database is tightly coupled with programming language, then it looks like ORM but better. And it probably can also reduce CRUD biolerplate or N+1 issue etc.
Related, there is SpacetimeDB that make backend run within database, and the backend code is highly coupled with SpacetimeDB's own API