GraphQL Interview Questions


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If you want to be prepared for your next interview. Read our top GraphQL interview questions and make sure you ace your next interview. Let’s start.

What is GraphQL?

GraphQL is an open source data query and manipulative language developed by Facebook. It is used to make API fast and user friendly. It allows developer to develop APIs that fetch data from multiple sources in a single call.

Explain the brief history of GraphQL Language.

Facebook developed the GraphQL language for its internal solution for mobile applications. The main reason behind developing this language is to optimize REST API calls by providing an efficient alternative to typical REST API.

What is Authentication in GraphQL?

Authentication is a mechanism through which you can identify the existence of valid user. It is used when user is try to login into the application with a username and password. You can implement authentication with common patterns like OAuth, which stands for Open Authorization. 

What is Authorization in GraphQL?

Authentication is a mechanism through which you give permissions to the authenticated users in your application. In GraphQL, you can delegate the authorization in business logic that describes whether the user has the permission of accessing or performing an action. 

What are the features of Authentication in GraphQL?

A GraphQL Authentication must have the following features:

  • It must protect the part of schema not all of it.
  • It must be able to authenticate schema on field level
  • It must provide the context of currentUser to the resolvers
  • Authentication logic must be hidden from the resolvers

What are the features of Authorization in GraphQL?

A GraphQL Authorization must have the following features:

  • It must be able to protect fields with custom rules and permissions
  • It must protect part of schema with a group of custom logics
  • The custom rules must not be bind with any resolver or depend on it

How to validate JSON Result in GraphQL Language?

An ideal GraphQL must return JSON object with a root element called data. If there is another root element, this will give you an idea that the query is failed or partially failed to send the result. Here is an example of the JSON result in error state:


  “data” : { … } , 

  “errors” : [ … ] 



How do you handle Server Side Caching in GraphQL Language?

The biggest challenge in GraphQL is to maintain the server side caching as compared to REST. In REST API, it is comparatively easy to implement caching in it as you can cache data for each end-point since the data stricture does not change in it. Nevertheless, in GraphQL, the subsequent call is not known and clear, therefore, it is difficult to handle the caching in it.

What type of response you get in GraphQL Language?

In GraphQL, whenever a client requests something from the server, it sends the response in JSON format.

What is Over Fetching in GraphQL Language?

In GraphQL, over fetching is a condition in which the requested client gets more data or extra data than requested. If the response has more data, it will increase the payload size.

What is Under Fetching in GraphQL Language?

In GraphQL, under fetching is a condition in which the requested client does not get enough data and you need to send multiple or subsequent calls to get the desired data.

How can you overcome the issues of over fetching and under fetching in GraphQL Language?

The issues in over fetching and under fetching are due to performance issues and occur when you have to manage and maintain multiple end points to get the response. GraphQL allows you to request the specific data from the server by specifying the exact result that you will need in the response from the server.


What are the advantages of GraphQL over REST API?

The following significant advantages of GraphQL makes it unique and robust in API:

  • In GraphQL, there is just a single end point, unlike REST that has many end points. This feature makes it more effective as there is no need to use the resources for various end points.
  • In GraphQL, you can get the complex result set in a single call, whereas on the other hand, REST needs multiple calls to send the complex set of result.
  • In GraphQL, you can send the multiple data response format, whereas you can only have one JSON format in REST API.
  • The speed of development is faster in GraphQL.
  • In GraphQL, you can have a consistent response across all the platforms, whereas, it is very hard to get consistency in REST API.
  • In GraphQL, you cannot have caching system by default and can manage it manually, whereas, REST provides caching automatically.

What is the main difference between GraphQL and REST?

The main difference between GraphQL and REST is that GraphQL is a language whereas REST is a web service API.

Which database can be used with GraphQL?

The GraphQL can be used with both SQL and NoSQL Databases.

Can you use GraphQL in offline mode?

GraphQL is designed to work in online mode. You can use some libraries such as Apollo or Relay to achieve the offline mode, but there is not a proper standardized way of doing work in an offline mode.

What is GraphiQL?

GraphiQL is used to facilitate the developer to have a UI representation of GraphQL. It is a browser-supported extension to make the use of usage of GraphQL easy and user friendly. It allows you to see the errors at run time.

What are the major operations of GraphQL?

The GraphQL supports three types of operations, i.e. query, mutation and subscription.

  • Query: It is used to request the data and is only a read operation.
  • Mutation: It is used to write operations.
  • Subscription: It is used to listen for any data changes.

Can you host a GraphQL Server Online?

You can use server-side programming language such as Node.js or Python to create a GraphQL Server and allow hosting on it.


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