GraphQL Interview Questions in 2024

GraphQL Interview Questions

GraphQL, developed by Facebook, has become a popular data query and manipulation language for APIs, known for allowing clients to request exactly what they need and nothing more. In 2024, interview questions for roles involving GraphQL are designed to assess a candidate’s technical proficiency with GraphQL, understanding of its use cases, and integration skills with other technologies. Here’s a guide on typical questions you might encounter during an interview for a position involving GraphQL and how to prepare effectively.

What are GraphQL Interview Questions?

GraphQL interview questions often focus on your understanding of the GraphQL architecture, its benefits over REST APIs, and your experience in implementing GraphQL in various applications. These questions can range from basic concepts to complex queries and mutations, and schema design.

Most Common GraphQL Interview Questions

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What is GraphQL and how does it differ from REST?

This fundamental question tests your understanding of GraphQL’s core concepts and advantages over traditional REST APIs. Example Response: “GraphQL is a query language for APIs and a runtime for executing those queries by using a type system you define for your data. Unlike REST, which requires loading from multiple URLs, GraphQL APIs get all the data your app needs in a single request. Apps using GraphQL can be quick even on slow mobile network connections. GraphQL also allows clients to request exactly what they need, making it more efficient than REST, which returns a fixed data structure.”

Can you explain the concept of a Query and a Mutation in GraphQL?

This question assesses your understanding of the fundamental operations in GraphQL. Example Response: “In GraphQL, a Query is used to fetch data in a read-only fashion, similar to a GET request in REST. Queries are meant to retrieve data without causing side effects. On the other hand, a Mutation is used to modify server-side data and represents operations that might change or mutate data, similar to POST, PUT, or DELETE in REST. Mutations are defined in the schema and include necessary input data.”

How do you handle errors in a GraphQL API?

Understanding error handling in GraphQL is crucial for building robust applications. Example Response: “In GraphQL, errors are handled by returning an errors field in the response, which is an array of error objects. Each error object typically includes a message, locations of the error in the query, and a path to the data that triggered the error. On the server side, I ensure that errors are logged for diagnostics and that sensitive error details are not exposed to the client, adhering to security best practices.”

Describe how you would design a schema in GraphQL.

This question explores your ability to design effective and scalable GraphQL schemas. Example Response: “When designing a GraphQL schema, I start by defining types and relationships that reflect the business domain. I ensure that each type has fields that are necessary for the application, and I define resolvers for these fields where complex data fetching logic is required. I also use input types for mutations to handle data creation and updates efficiently. Additionally, I consider using interfaces or union types if there’s a need to support polymorphic types.”

What are the challenges of using GraphQL and how do you overcome them?

Discussing challenges shows your depth of experience and problem-solving skills. Example Response: “One challenge with GraphQL is performance issues related to over-fetching or deep queries that can lead to the ‘n+1 queries problem’. To overcome this, I use batching and caching mechanisms like DataLoader to batch multiple requests into a single request. Another challenge is maintaining security, for which I implement query depth limiting, rate limiting, and validate inputs to avoid malicious queries and ensure the API’s robustness.”

How do you optimize queries in GraphQL?

This question checks your ability to enhance the performance of GraphQL implementations. Example Response: “To optimize queries in GraphQL, I focus on several strategies: First, I ensure that queries are only fetching the data that is needed by the client. I also use persistent queries to restrict clients to predefined queries, which can improve performance and security. On the server side, I use caching of common queries and optimize resolver functions to minimize database calls, especially in resolving nested objects.”

How to Get Prepared for GraphQL Interview Questions

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Review GraphQL Concepts

Ensure you have a solid understanding of GraphQL operations, schema design, types, and best practices.

Practical Experience

Hands-on experience is crucial. Work on projects using GraphQL or set up a demo project to familiarize yourself with writing schemas, queries, and mutations.

Understand Integrations

Know how GraphQL integrates with other technologies, particularly how it is implemented on the server side using popular frameworks like Apollo or Relay.

Keep Updated

Stay informed about the latest developments and best practices in the GraphQL community.

Prepare Problem-Solving Examples

Be ready to discuss past scenarios where you implemented or solved issues using GraphQL, highlighting your thought process and outcomes.

Develop Questions

Prepare questions about the company’s use of GraphQL, such as how they handle data fetching strategies or security concerns, to show your interest and engagement during the interview.


Preparing for a GraphQL interview involves demonstrating your technical knowledge, practical skills in schema design and query optimization, and your ability to solve common problems associated with GraphQL. By effectively preparing for these common questions, you can showcase your expertise and readiness for a role involving GraphQL.

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