Strapi v4 - Graphql database interaction

In Strapi v3, default graphql resolvers were just calling API controllers to retrieve / mutate data.
After I installed beta 4 and tried few graphql queries, I found out that graphql doesn’t call collection data controller, neither does it call a collection data service.
So I’m wondering, how does graphql get to the data in strapi v4, does anyone have an idea?