You use the best tool and write code at the appropriate layer. I don’t think anyone suggests writing the entire application in the database (though you can with

You use the best tool and write code at the appropriate layer. I don’t think anyone suggests writing the entire application in the database (though you can with Oracle). UI and interfacing with external services will most likely prove simpler to implement in an application layer. Google and Stripe don’t have SDKs for Postgres. If the application needs a relational database at all it makes sense to get the most value out of the RDBMS.