API / Apollo Gateway Interview questions
What is a supergraph in Apollo Federation?
The supergraph is the single composed schema that results from merging every subgraph's schema through Federation's composition algorithm. It's the schema clients actually query against — they have no visibility into how many subgraphs sit behind it or how the data is split.
Beyond the merged type definitions, the supergraph schema also embeds routing metadata: which subgraph owns which field, and how entities join across services. That metadata is what lets the gateway or router build an accurate query plan for any incoming operation without guessing at runtime.
In managed federation, this composed supergraph schema is generated by GraphOS and delivered to running gateway/router instances automatically whenever a subgraph publishes a schema change.
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