If you have an application that is mostly just relational data, and if all the business logic is easy to write as SQL, then PostgREST is essentially a no-code R

If you have an application that is mostly just relational data, and if all the business logic is easy to write as SQL, then PostgREST is essentially a no-code REST API for your database, and it's way less effort than anything you'd do in Java/Golang/Python/Rust/C++/whatever. Plus it's easier to get concurrency right if you push as much of the business logic into the RDBMS as SQL or similar.