GraphQL Federation Gateway

Apollo Federation uses a standardized entity model where each implementing service declares which types and fields it owns, and the gateway automatically resolves cross-service relationships at query time. Earlier schema stitching required manual merge resolvers and custom conflict resolution, which became unwieldy as the number of services grew.

Apollo provides the @apollo/gateway npm package for Node.js and the Apollo Router, a high-performance gateway written in Rust released in 2022. Both support the Apollo Federation v2 specification, which simplified the original v1 entity resolution model and added better support for features like directive composition.

Yes, you can wrap REST APIs, gRPC services, or direct database connections behind a thin GraphQL service that then joins the federation as a subgraph. Tools like Apollo Server, Mercurius for Fastify, and Spring for GraphQL all support building subgraphs regardless of the underlying backend technology.

If a subgraph is unavailable, queries that touch only unaffected types still succeed because the gateway routes field resolution independently per service. However, any query requesting fields owned by the downed subgraph will return a partial result with errors for those fields, and clients can use the @skip and @include directives to degrade gracefully.