> Another problem GraphQL hasn't tackled (afaik) is polymorphism. You can say "hey give me this person" or "give me this company", but what if you want a customer that can be either a person or a company?

http://graphql.org/learn/schema/#interfaces

  searchPersonOrCompany(name: "abc") {
    ... on User {
     first_name
     last_name
    }
    ... on Company {
     business_name
    }
  }

As for the undetermined depths problem -- I agree to an extent.

GraphQL can't return depths without you querying for it unless one of the field is a JSON blob.. but at the same time, I like that it does that.

In your example of menu w/ submenus, I think I would prefer to load the first 2 level, then preload level 3 when level 2 is activated, and preload level 5 when level 4 is activated, and so on.

Apollo makes this quite easy.

If I want to get all levels of an arbitrarily nested tree, I just query for all of the objects that are in the tree in a flat array and then reconstruct the tree on the client side using the parent/child Ids.

This is similar to what I would have to do server side if I were using SQL to get the data and then processing it to return a tree in JSON.

If I know how deep the tree will be (and it is only two or three levels) I query it directly with graphql