What is the GraphQL Mesh library?

GraphQL Mesh (by The Guild) is a tool that generates a unified GraphQL API over any data source — REST APIs, gRPC services, SOAP, GraphQL, database ORM, OpenAPI specs, and more — without writing resolvers manually. It reads the source schema/spec (OpenAPI YAML, gRPC proto, GraphQL SDL), generates a GraphQL layer on top, and serves it as a single endpoint. Key features: (1) Transforms: rename types, filter fields, add resolvers, change nullability. (2) Merging: combine multiple sources into one schema (like stitching but declarative). (3) Type safety: generates TypeScript types for all sources. (4) Plugins: caching, mocking, rate limiting, auth. (5) Federation compatibility: can produce Federation-compatible subgraphs. Configuration is YAML-based: .meshrc.yaml. Excellent for wrapping legacy REST APIs in GraphQL without extensive development, or building a unified API layer over a microservice landscape.