Mercurius

Mercurius is a GraphQL adapter for Fastify, providing high-performance GraphQL server capabilities including query caching, automatic loader integration to avoid N+1 queries, JIT compilation via graphql-jit, subscriptions, federation support, and a gateway implementation. It is the recommended GraphQL solution for Fastify applications. Current stable version is 16.9.0, released under an active development cadence. It requires Node.js >=20.9.0 or >=22.0.0 and peer dependency graphql ^16.0.0. Key differentiators: tight integration with Fastify, built-in loaders, subscriptions, and federation support.