GraphQL Questions and Answers for Viva

Answer-1: GraphQL is a query language for APIs and a runtime for executing those queries by using a type system you define for your data.

Answer-2: REST relies on multiple endpoints for different resources, while GraphQL uses a single endpoint and allows clients to request only the data they need.

Answer-3: A resolver in GraphQL is a function responsible for returning a value for a specific field in a query.

Answer-4: A schema defines the structure of the GraphQL API, including types, queries, mutations, and subscriptions.

Answer-5: Queries in GraphQL are used to fetch data from the server, and they specify exactly what fields and data are needed.

Answer-6: Mutations in GraphQL are used to modify data, similar to POST, PUT, and DELETE in REST APIs.

Answer-7: Subscriptions in GraphQL are used to maintain a real-time connection to the server, allowing clients to receive updates when data changes.

Answer-8: GraphQL allows clients to fetch exactly the data they need in a single request, reducing over-fetching and under-fetching.

Answer-9: A field in GraphQL represents a piece of data that a query can request from the server. Fields are defined in types.

Answer-10: A query fetches data, while a mutation is used to modify data on the server.

Answer-11: A type system in GraphQL defines the structure and relationships of the data that can be queried, including scalars, objects, and enums.

Answer-12: Scalar types are the basic types in GraphQL, such as String, Int, Float, Boolean, and ID.

Answer-13: An object type in GraphQL represents a complex object with fields that can be queried. Each field in an object type can have its own type.

Answer-14: The ID type is a special scalar type in GraphQL used to represent unique identifiers for objects.

Answer-15: In GraphQL, errors are returned as part of the response object in a special errors field. Each error contains a message and other details.

Answer-16: Fragments in GraphQL allow you to reuse parts of a query. They are like subqueries that can be included in multiple places.

Answer-17: Variables in GraphQL allow you to parameterize your queries and pass dynamic values when executing them.

Answer-18: Authentication and authorization are typically handled by middleware or within the resolver functions. Common methods include JWT and API keys.

Answer-19: Pagination in GraphQL is often implemented using cursor-based pagination, where each result includes a cursor pointing to the next page.

Answer-20: A schema-first approach involves designing the GraphQL schema first, then generating the resolvers and the rest of the server logic based on the schema.

Answer-21: A synchronous resolver returns data directly, while an asynchronous resolver returns a promise and resolves it when the data is available.

Answer-22: Introspection is the ability to query the GraphQL schema itself to understand its structure and capabilities.

Answer-23: GraphQL supports batching requests through techniques like DataLoader, which allows for multiple queries to be executed in a single round trip.

Answer-24: A custom scalar type in GraphQL allows you to define your own data types with specific parsing and serialization rules.

Answer-25: Apollo Server is a popular open-source implementation of a GraphQL server that integrates with various backends, supports subscriptions, and provides features like caching and schema stitching.

Answer-26: Schema stitching allows you to combine multiple GraphQL schemas into a single unified schema, enabling a federated API.

Answer-27: Apollo Client is a library for managing GraphQL data in the client, handling queries, mutations, caching, and state management.

Answer-28: The @deprecated directive marks a field or type as deprecated, indicating it should no longer be used and will be removed in the future.

Answer-29: The @include directive allows conditional inclusion of fields based on a specified condition in the query.

Answer-30: The @skip directive allows conditional exclusion of fields based on a specified condition in the query.

Answer-31: GraphQL is a query language for APIs that focuses on flexible data retrieval, while SQL is a language for querying relational databases.

Answer-32: Rate limiting in GraphQL is typically handled at the server or gateway level by counting the number of requests made by clients over a given period.

Answer-33: Middleware in GraphQL can be used to handle cross-cutting concerns such as logging, authentication, caching, and rate limiting.

Answer-34: GraphQL allows clients to request exactly the data they need, reduces over-fetching and under-fetching, supports real-time updates with subscriptions, and uses a single endpoint for all interactions.

Answer-35: Queries are side-effect-free, meaning they do not modify data, while mutations are used to create, update, or delete data, causing side effects on the server.

Answer-36: Apollo Federation allows you to compose multiple GraphQL services into one data graph, enabling a federated architecture for scaling and managing GraphQL APIs.

Answer-37: GraphQL subscriptions enable real-time updates by maintaining an open connection between the client and server, pushing updates when data changes.

Answer-38: GraphQL prevents over-fetching by allowing the client to request only the data it needs in the query, avoiding unnecessary data transfer.

Answer-39: The @resolve directive allows customizing the way fields are resolved, enabling transformations or additional logic when fetching data.

Answer-40: DataLoader is used to batch and cache database queries, preventing redundant queries and improving performance.

Answer-41: GraphQL can integrate with multiple data sources by defining resolvers that fetch data from databases, REST APIs, or any other external services.

Answer-42: Pagination in GraphQL allows clients to retrieve large sets of data in smaller chunks using techniques like limit and offset or cursor-based pagination.

Answer-43: Optimistic UI allows the client to assume a mutation will succeed and immediately update the UI, while real-time updates push changes to the client through subscriptions.

Answer-44: A GraphQL playground is an interactive environment for testing and exploring GraphQL APIs, often provided as a web interface like Apollo Studio.

Answer-45: A custom directive in GraphQL allows you to define your own behavior for specific fields, like adding additional logic or transforming data.

Answer-46: The @client directive is used to query data from the local cache or client-side state, rather than from the server.

Answer-47: Circular dependencies in GraphQL can be managed by carefully structuring types and using fragment definitions to break cycles.

Answer-48: Performance issues in GraphQL can include N+1 query problems, excessive query complexity, and the need for batching and caching strategies.

Answer-49: Testing a GraphQL API involves writing unit and integration tests for queries, mutations, and resolvers, often using tools like Jest or Apollo Server's test utilities.

Answer-50: Query optimization can be achieved by limiting the number of fields requested, using pagination, batching requests, and employing caching mechanisms like DataLoader.