GraphQL Federation enables teams to own their GraphQL services while exposing a unified API. The gateway composes schemas from multiple subgraphs. Teams develop independently with clear boundaries.
Federation Concepts
Subgraphs define their portion of the overall schema. Entities are shared types across subgraphs. Reference resolvers fetch entity data from owning services. The router composes and executes queries.
- Define entities with @key directive for cross-service references
- Implement reference resolvers for entity hydration
- Use @external to reference fields from other subgraphs
- Extend types across service boundaries
- Plan schema ownership and boundaries carefully
Implementation Considerations
Federation adds complexity—ensure benefits justify costs. Plan entity ownership preventing circular dependencies. Monitor query plans for performance issues. Version schemas carefully across services.