I don't know if I completely understand what you are saying, my comment doesn't rely on multiple data stores. I'm talking about a web application with a single (say, SQL-based) datastore.

I am saying that without the full power of that data store on the client side (that is, an optimizable query language, update and insert statements) you will always be thrashing your API around to deal with chaotic UI needs.

If you do expose the full datastore functionality on the client side (which GraphQL is a move towards) then you have a different problem: you are exposing your datastore in a fundamentally insecure environment.

So you are screwed either way.