What is federation

GraphQL Federation is a way to build a GraphQL API that can be composed of multiple services.

GraphQL as an abstraction layer

GraphQL can be used as an abstraction between service consumers and backend services.

Instead of having each BFF server per version of application, you can have a single GraphQL layer acts as a pointer to any number of arbitrary backend services.

App -- BFF -- old service
App -- BFF -- ^
App -- BFF -- ^
App -- BFF -- another service
App -- BFF -- v
              new service

Below relies on a single GraphQL layer to be able to point to any number of arbitrary backend services.

App               old service
App               another service
App -- GraphQL -- ^
App               v
App               new service

This could eliminate hundreds of updates, deployments, and dependencies from moving the changes away from the backend services.