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GraphQL

GraphQL — Complete Query Lifecycle CLIENT & TRANSPORT Apollo Client React / Vue / Mobile Cache · Fragments Relay / URQL Pagination · Batching GraphQL over HTTP Queries · Mutations · Subscriptions SERVER & SCHEMA Schema Definition typeDefs · gql`` tag SDL · Code First Apollo Server Express / Hapi / Fastify Hot Chocolate (.NET) Type System: Object · Scalar · Enum · Interface · Union · Input Non-Null (!) · List [] · Custom Scalars RESOLVERS & DATALOADER Root Resolver Query.users · Mutation.createUser Nested Resolver User.posts · Post.author DataLoader (Batching + Caching · Solves N+1) DATA SOURCES SQL Database PostgreSQL · MySQL Prisma · TypeORM MongoDB Mongoose / Driver MongoDB Atlas REST APIs RESTDataSource · fetch External services Cache Redis · In-Memory Response caching SUBSCRIPTIONS WebSocket graphql-ws · Apollo WS Event Driven Kafka · Redis · NATS SECURITY & BEST PRACTICES Depth Limiting Prevent deep nesting Complexity Analysis Cost per field Rate Limiting Per user / IP / API key Persisted Queries Allowlist approach TOOLS & ECOSYSTEM GraphiQL IDE Interactive explorer Apollo Studio Schema registry · Metrics Code Generation GraphQL Codegen Federation Apollo Federation · Schema stitching Testing Integration · Contract Auth JWT · OAuth · RBAC INTEGRATION PATTERNS GraphQL Gateway → Microservices → Databases BFF (Backend for Frontend) Schema Stitching · Apollo Federation GraphQL + Kafka + SignalR Events