GraphQL Interview Questions and Answers for experienced

0
100 GraphQL Interview Questions and Answers

  1. What is GraphQL and how does it differ from REST?

    • Answer: GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. Unlike REST, which uses predefined endpoints returning fixed data structures, GraphQL allows clients to request precisely the data they need, reducing over-fetching and under-fetching. It uses a strongly-typed schema to define the data available and how to access it, enabling better tooling and discoverability.

  2. Explain the concept of a GraphQL schema.

    • Answer: A GraphQL schema is a formal description of the data available through your GraphQL API. It's written using the Schema Definition Language (SDL) and defines types (e.g., scalars like Int, String, Boolean; objects; interfaces; unions; enums), their fields, and relationships between them. The schema acts as a contract between the client and the server, ensuring type safety and predictable data.

  3. What are resolvers in GraphQL?

    • Answer: Resolvers are functions that fetch data for a given field in a GraphQL schema. They connect the schema's abstract definition to the underlying data sources (databases, APIs, etc.). Each field in the schema has an associated resolver that determines how to retrieve the data for that field.

  4. Describe different GraphQL scalar types.

    • Answer: Common scalar types include `Int`, `Float`, `String`, `Boolean`, `ID`. Scalars represent primitive values and are not further resolvable. Custom scalar types can be defined to handle more complex data like dates, URLs, or specific data formats.

  5. What are object types in GraphQL?

    • Answer: Object types represent complex data structures with multiple fields. Each field within an object type can be a scalar, another object type, or a list of either.

  6. Explain interfaces and unions in GraphQL.

    • Answer: Interfaces define a contract that object types can implement, specifying shared fields. Unions allow a field to return one of several object types, useful when a field can represent different kinds of data.

  7. How do you handle pagination in GraphQL?

    • Answer: Pagination is typically handled by adding arguments to your queries (e.g., `first`, `after`, `last`, `before`). The resolver then uses these arguments to fetch a subset of the data and return information for fetching the next or previous page.

  8. What are subscriptions in GraphQL?

    • Answer: Subscriptions provide a way to receive real-time updates from the server. When a change occurs in the data, the server pushes the updated data to the subscribed clients.

  9. Explain the concept of GraphQL fragments.

    • Answer: Fragments allow you to reuse portions of a GraphQL query across multiple operations. They are especially useful for selecting a subset of fields from an object type used in different parts of your query.

  10. How do you handle errors in GraphQL?

    • Answer: GraphQL errors are typically returned within the response, providing detailed information about the error. Proper error handling includes providing meaningful error messages and distinguishing between client-side and server-side errors.

  11. What are some popular GraphQL clients?

    • Answer: Popular GraphQL clients include Apollo Client (JavaScript), Relay (React), and others specific to various programming languages.

  12. What are some popular GraphQL servers?

    • Answer: Popular GraphQL servers include Apollo Server, Hasura, and others depending on the backend technology.

  13. Explain the use of directives in GraphQL.

    • Answer: Directives provide a way to modify the execution of a GraphQL query or schema. Common directives include `@skip` and `@include`, allowing conditional inclusion or exclusion of fields.

  14. How do you implement authorization in a GraphQL API?

    • Answer: Authorization is typically handled within the resolvers, checking the user's permissions before accessing and returning data. This might involve using JWTs, roles, or other authorization mechanisms.

  15. How do you handle schema evolution in GraphQL?

    • Answer: Schema evolution requires careful planning and consideration of backward compatibility. Techniques like deprecating fields, adding new fields, and versioning the schema can help manage changes without breaking existing clients.

  16. Explain the concept of DataLoader in GraphQL.

    • Answer: DataLoader is a utility for batching and caching data fetching, improving performance by reducing the number of calls to underlying data sources.

  17. What is introspection in GraphQL?

    • Answer: Introspection allows clients to query the GraphQL schema itself, obtaining information about available types, fields, and their descriptions. This is crucial for tooling and client-side code generation.

  18. Describe different ways to cache data in a GraphQL application.

    • Answer: Caching can be implemented at various levels – client-side caching using libraries like Apollo Client, server-side caching using Redis or Memcached, and database-level caching.

  19. How do you test a GraphQL API?

    • Answer: Testing a GraphQL API involves using tools and techniques like unit testing for resolvers, integration testing for interactions between resolvers and data sources, and end-to-end testing for the entire API flow.

Thank you for reading our blog post on 'GraphQL Interview Questions and Answers for experienced'.We hope you found it informative and useful.Stay tuned for more insightful content!