Top 79 GraphQL Interview Questions & Answers (2026)

01 What is GraphQL? 02 What are the main differences between GraphQL and REST? 03 What is a GraphQL schema? 04 What is a GraphQL query? 05 What is a GraphQL mutation? 06 What is a GraphQL subscription? 07 What are GraphQL types? 08 What is the difference between ! (non-null) and nullable fields in GraphQL? 09 What is a GraphQL resolver? 10 What is the GraphQL Schema Definition Language (SDL)? 11 What is GraphQL introspection? 12 What is GraphiQL? 13 What are GraphQL variables? 14 What are GraphQL fragments? 15 What are inline fragments in GraphQL? 16 What are GraphQL directives? 17 What is the difference between a query and a mutation in terms of execution? 18 What is the N+1 problem in GraphQL? 19 What is DataLoader and how does it solve the N+1 problem? 20 What is the Apollo Client? 21 What is Apollo Server? 22 What is a GraphQL endpoint? 23 What is the GraphQL response format? 24 What are enum types in GraphQL? 25 What are input types in GraphQL? 26 What are interfaces in GraphQL? 27 What are union types in GraphQL? 28 What is schema-first vs code-first GraphQL development? 29 What is the context object in GraphQL? 30 What is the root value in GraphQL? 31 How does error handling work in GraphQL? 32 What is the info argument in a GraphQL resolver? 33 What is persisted queries in GraphQL? 34 What are custom scalars in GraphQL? 35 What is GraphQL Federation? 36 What is the difference between query, mutation, and subscription operations? 37 How do you handle file uploads in GraphQL? 38 What is the difference between REST and GraphQL in terms of over-fetching and under-fetching? 39 How do you authenticate in GraphQL? 40 What is the args argument in a GraphQL resolver?

01 How do you implement pagination in GraphQL? 02 What is the Relay specification in GraphQL? 03 How do you implement authorization in GraphQL resolvers? 04 What is graphql-shield and how does it work? 05 How do you implement real-time subscriptions with GraphQL? 06 What is schema stitching in GraphQL? 07 What is a GraphQL gateway? 08 What is the Apollo Cache and how does normalized caching work? 09 How do you handle optimistic UI in GraphQL with Apollo? 10 What are Apollo Client hooks and how do you use them? 11 What is the difference between network-only, cache-first, and cache-and-network fetch policies? 12 How do you update the Apollo cache after a mutation? 13 What is the graphql-tag (gql) utility? 14 What is query depth limiting in GraphQL and why is it important? 15 What is query complexity analysis in GraphQL? 16 What is the difference between Apollo Server v3 and v4? 17 What is urql and how does it compare to Apollo Client? 18 What is Relay and how does it differ from Apollo Client? 19 What is the GraphQL over HTTP spec? 20 How do you implement a DataLoader with batching and caching? 21 What are Apollo Client's reactive variables? 22 What is the @client directive in Apollo Client? 23 What is deferred query execution in GraphQL? 24 How do you implement field-level caching with cache hints in GraphQL?

01 What is Apollo Federation v2 and how does the supergraph work? 02 How do you implement entity resolution in Apollo Federation? 03 What are the security vulnerabilities specific to GraphQL? 04 How does the GraphQL query planning and execution pipeline work? 05 What is the @defer and @stream directive and how do they work? 06 How do you design a scalable GraphQL schema? 07 What are the best practices for error handling in GraphQL APIs? 08 What is the GraphQL Mesh library? 09 How do you implement schema evolution and versioning in GraphQL? 10 What is the GraphQL Codegen tool and how is it used? 11 What is GraphQL subscriptions with WebSocket protocol graphql-ws vs subscriptions-transport-ws? 12 How do you implement distributed tracing for GraphQL? 13 What are the trade-offs of using GraphQL vs REST for different use cases? 14 How do you test GraphQL APIs effectively? 15 What is operation complexity and how does it relate to rate limiting GraphQL APIs?