What is Schema Stitching vs Schema Federation in depth?

Stitching relies on a centralized gateway imperative configuration. Federation pushes configuration down to autonomous subgraphs.

Stitching requires the Gateway developer to write code that maps extend type User and defines how to query the target service. Federation uses the @key directive. A subgraph says type User @key(fields: "id"), and the Gateway automatically knows how to construct an entity execution plan using _entities queries without custom gateway logic.