Relay Compiler

The Relay Compiler is the build-time tool for the Relay GraphQL client, currently at stable version 20.1.1. It transforms GraphQL fragments and queries defined in JavaScript/TypeScript files into optimized runtime artifacts, including persisted query mappings. Released under a regular cadence with major updates every few months, it provides strict schema validation, type-safe fragment composition, and support for directives like @alias, @catch, and @preloadable. Key differentiators include deep integration with React via Suspense and load-as-you-render patterns, zero-runtime overhead from compiled operations, and strong typing via generated Flow or TypeScript definitions. Unlike Apollo's codegen, Relay Compiler enforces a global schema and prevents over-fetching by design through its colocation model.