GraphQL Federation Pattern

Using Apollo Federation, you can compose the Shopify Storefront API alongside your own GraphQL services—such as a reviews service or inventory service—into a single supergraph that clients query through one gateway. Each service annotates its schema with directives like @key and @extends, and the gateway resolves fields across services automatically so the client sees one unified API.

Schema stitching was Apollo's earlier method of merging schemas by manually writing field-level resolvers that fetched from different services, but it was deprecated in favor of Federation. Federation uses a declarative model where each subgraph publishes its own schema with federation directives, and the Apollo Gateway handles query planning and distributed execution automatically.

Yes, alternatives exist, including the open-source Apollo Router written in Rust, which can run as a standalone gateway without Apollo Studio. Other frameworks like Mercurius for Fastify in the Node.js ecosystem also support federation-style composition, though Apollo's tooling remains the most mature and widely adopted.

Federation introduces an extra network hop between the gateway and each subgraph, which adds latency compared to a monolithic GraphQL server, and the gateway must build query plans that can span multiple services per request. However, it enables independent team deployment and scaling of services like checkout versus catalog, which typically outweighs the overhead for large platforms.