GraphQL Interview Questions and Answers for internship

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GraphQL Internship Interview Questions and Answers

  1. What is GraphQL?

    • Answer: GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. It allows clients to request exactly the data they need and nothing more, improving efficiency and reducing over-fetching compared to REST.

  2. What are the key differences between GraphQL and REST?

    • Answer: GraphQL uses a single endpoint, while REST typically uses multiple endpoints. GraphQL allows clients to specify exactly what data they need, reducing over-fetching (getting more data than needed) and under-fetching (requiring multiple requests to get all necessary data), unlike REST. GraphQL uses a strongly-typed schema for improved data validation and introspection, whereas REST relies on less formal data structures and documentation.

  3. Explain the concept of a GraphQL schema.

    • Answer: A GraphQL schema is a strongly-typed description of the data available in your API. It defines the types of objects, their fields, and the relationships between them. This schema acts as a contract between the client and the server, ensuring data consistency and enabling static analysis tools.

  4. What are queries in GraphQL? Provide an example.

    • Answer: Queries are used to fetch data from a GraphQL server. They specify the fields that the client wants to retrieve. Example: `query { hero { name, appearsIn } }` This query requests the name and appearances of a hero.

  5. What are mutations in GraphQL? Provide an example.

    • Answer: Mutations are used to modify data on the server, such as creating, updating, or deleting data. Example: `mutation createReview($episode: Episode!, $review: String!) { createReview(episode: $episode, review: $review) { stars, commentary } }` This mutation creates a new review.

  6. What are subscriptions in GraphQL?

    • Answer: Subscriptions enable real-time updates from the server to the client. When data changes on the server that matches the subscription's criteria, the client receives an update immediately.

  7. Explain the concept of resolvers in GraphQL.

    • Answer: Resolvers are functions that are responsible for fetching the data for a particular field in a GraphQL schema. They connect the schema to the underlying data sources.

  8. What are fragments in GraphQL?

    • Answer: Fragments allow you to reuse parts of a query. They are especially useful when you need to fetch the same set of fields from multiple types.

  9. What are variables in GraphQL? Why are they useful?

    • Answer: Variables allow you to pass dynamic values to your queries and mutations. This makes your queries more reusable and prevents hardcoding values.

  10. What is introspection in GraphQL?

    • Answer: Introspection allows clients to query the GraphQL schema itself, providing information about available types, fields, and their arguments. This is useful for tools that generate client code or documentation.

  11. How do you handle errors in GraphQL?

    • Answer: GraphQL errors are typically returned within the response, often including a message, location, and path indicating the source of the error. Proper error handling involves logging errors, returning user-friendly messages, and ensuring the API remains responsive.

  12. What are some popular GraphQL clients?

    • Answer: Apollo Client, Relay, urql are some popular GraphQL clients.

  13. What are some popular GraphQL servers?

    • Answer: Apollo Server, GraphQL Yoga, and Express-GraphQL are some popular GraphQL servers.

  14. Describe a time you had to debug a GraphQL query or mutation.

    • Answer: [Describe a specific scenario, focusing on your problem-solving approach and the tools/techniques you used. Mention specific errors encountered, if any.]

  15. Explain your understanding of schema stitching in GraphQL.

    • Answer: Schema stitching combines multiple GraphQL schemas into a single unified schema. This allows you to integrate different data sources and microservices under a single API.

  16. What is the purpose of using directives in GraphQL?

    • Answer: Directives provide a way to add extra instructions to your GraphQL queries and schemas. They can influence how a query is executed or how a field is resolved.

  17. Explain the concept of pagination in GraphQL.

    • Answer: Pagination is a technique to fetch large datasets efficiently by retrieving only a subset of data at a time. This improves performance and avoids overwhelming the client with massive amounts of data.

  18. How would you handle authorization and authentication in a GraphQL API?

    • Answer: Authentication often involves using JWTs or other methods to verify the user's identity. Authorization typically involves checking if a user has the necessary permissions to access specific data or perform certain actions, often implemented within resolvers.

  19. What are some best practices for designing a GraphQL schema?

    • Answer: Keep types cohesive, avoid overly nested structures, use descriptive field names, handle errors gracefully, and version your schema appropriately.

  20. What are the benefits of using a GraphQL schema?

    • Answer: Provides a clear contract between client and server, facilitates better tooling and documentation, improves code maintainability, and enables static analysis.

  21. What tools or libraries have you used for working with GraphQL?

    • Answer: [List tools and libraries. Examples: Apollo Client, Apollo Server, GraphiQL, GraphQL Code Generator, etc.]

  22. How familiar are you with different GraphQL caching strategies?

    • Answer: [Discuss different caching techniques, such as client-side caching with Apollo Client, server-side caching with Redis, etc., and their trade-offs.]

  23. How do you ensure data consistency when using GraphQL?

    • Answer: Proper schema design, well-defined resolvers, and transactional operations (where applicable) are key to ensuring data consistency.

  24. Explain your understanding of DataLoader in the context of GraphQL.

    • Answer: DataLoader helps batch and cache database calls, significantly improving performance by reducing the number of database queries.

  25. What are some common performance considerations when working with GraphQL?

    • Answer: Overly complex queries, N+1 problem, inefficient resolvers, lack of caching, and inefficient data fetching can impact performance. Proper indexing and database optimization are also important.

  26. How would you approach designing a GraphQL API for a specific application (e.g., e-commerce)?

    • Answer: [Outline a potential schema, considering key entities like products, users, orders, and their relationships. Discuss your approach to pagination, error handling, and data modeling.]

  27. What are your thoughts on the future of GraphQL?

    • Answer: [Discuss potential trends like Federation, improved tooling, wider adoption, and integration with other technologies.]

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