This is basically what most rdbmses have been offering for the last 20 years. Oracle rdbms is in fact an application server, and best practice is to have an app

This is basically what most rdbmses have been offering for the last 20 years. Oracle rdbms is in fact an application server, and best practice is to have an app layer built using plsql package through which you access all the data. More than 20 years ago I actually used it as a true application server, where the database application layer would even generate all the HTML code required to displayed your app ui. And with database schemas you have proper sandboxing.