what do datatypes have to do with this. For both PostgREST and any other api layer the situation is the same. The data sits in the db/tabes (so both parties are restricted to the types available in pg) and on the other end you need to output json. The fact that you can have some "smart" internal datatypes in other api layers has 0 advanteges, both systems have to basically take data from the db and display it as json, the intermediate types are irelevant