I'm building my first PHP web app with AngularJS as the front end and utilizing Slim to create a REST-like API for the web app to interface with. I'm finding that the majority of my code I'm writing is SQL, there is very little PHP logic in the backend except for sessions and input validation.
Each endpoint might have 1-2 unique queries it uses to get the data it returns to the client. A few endpoints utilize 3-5 queries for some complex version management, historical data modifications, and validation bits.
Is it normal for a web app to have a really SQL heavy backend? Are there best practices for this sort of thing? I'm about 70% SQL 30% PHP right now.