What is GraphQL Federation?

GraphQL Federation is an architectural approach that combines schemas owned by different services into one higher-level schema. Product, user, order, and billing domains can remain with separate teams while clients talk to one GraphQL API.

Each service runs as a subgraph with its own types and resolvers. A router or gateway receives a query, splits it into sub-queries, sends them to the right services, and merges the results into a single response.

How Does It Work?

Federation connects services through shared entity definitions. For example, a product service may own the core Product fields, while a reviews service adds review fields linked to the same product entity. The router plans which part of the query comes from each subgraph.

If schema ownership is unclear, federation becomes difficult quickly. Naming, versioning, authorization, query cost, and backward compatibility need explicit agreements between teams.

Business Use

GraphQL Federation is used in larger products where a single API team would become a bottleneck. Domain teams can work within their microservice boundaries while customer-facing applications consume one data graph.

Not every GraphQL project needs federation. For a small team and a handful of data sources, one straightforward schema is easier to operate. Federation starts to pay off when service ownership and team boundaries are genuinely separate.