Top 50 GraphQL Interview Questions & Answers (2026)

01 What is GraphQL and who created it? 02 What is the difference between GraphQL and REST? 03 What is a GraphQL query? 04 What is a GraphQL mutation? 05 What is a GraphQL subscription? 06 What is the GraphQL Schema Definition Language (SDL)? 07 What are the scalar types in GraphQL? 08 What is an object type in GraphQL? 09 What is a resolver function in GraphQL? 10 What are variables in GraphQL queries? 11 What are arguments in GraphQL? 12 What are fragments in GraphQL? 13 What are inline fragments in GraphQL? 14 What are directives in GraphQL? 15 What is an operation name in GraphQL? 16 What are aliases in GraphQL? 17 What are the three root types in GraphQL? 18 What is the difference between nullable and non-null types in GraphQL? 19 What is the GraphQL Playground and introspection? 20 What is over-fetching and under-fetching in REST and how does GraphQL solve them?

01 What is the N+1 problem in GraphQL and how does DataLoader solve it? 02 What are persisted queries in GraphQL? 03 What is the difference between schema-first and code-first GraphQL approaches? 04 What are the pagination strategies in GraphQL? 05 How is authentication handled in GraphQL? 06 How do you implement field-level authorization in GraphQL? 07 What are custom scalars in GraphQL? 08 What is the difference between Input types and Object types in GraphQL mutations? 09 How does error handling work in GraphQL? 10 What is the difference between union types and interface types in GraphQL? 11 What is schema stitching versus Apollo Federation in GraphQL? 12 How do GraphQL subscriptions work over WebSocket? 13 What is query depth limiting in GraphQL? 14 What is query complexity analysis in GraphQL? 15 What is Apollo Client and how does it work with GraphQL? 16 What is graphql-tag and DocumentNode? 17 How do field resolvers work with the parent object in GraphQL? 18 What are schema extensions in GraphQL? 19 What is batch loading in GraphQL and how does it improve performance? 20 What are GraphQL enums?

01 What is Apollo Federation and how do subgraphs, gateways, and directives like @key and @extends work? 02 What is incremental delivery in GraphQL with @defer and @stream? 03 How do you implement query cost analysis and rate limiting in a production GraphQL API? 04 What is schema evolution and deprecation strategy in GraphQL? 05 What is the Relay specification for GraphQL — Node interface, Connection/Edge pagination? 06 How do you implement distributed tracing across GraphQL resolvers? 07 How does client-side caching work with Apollo Client's normalized cache? 08 How do you scale GraphQL subscriptions using Redis pub/sub? 09 What is schema composition and conflict detection in Apollo Federation? 10 What is a schema registry and GraphQL governance at scale?