Commonly Asked REST API Interview Questions (With Answe

By Indeed Editorial Team

Published 17 April 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Representational state transfer (REST) application programming interface (API) is an architectural style that software developers use to enable communication between the server and client part of a product. Employers ask REST API interview questions to test your functional and operational understanding of the application programming interface in software development interviews. Knowing about the fundamentals of REST and essential job interview questions can help you prepare better for your next software development role. In this article, we discuss some commonly asked REST API interview questions and sample answers to give you an overview of what to expect in your interview.

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Common REST API interview questions

Knowing the answers to some of the common REST API interview questions can help you perform well in the interview. While these are standard questions, they can help enhance your understanding of critical concepts of REST APIs. Here are some common REST API questions and sample answers to help guide you in your preparation for a software development role:

What is REST API?

This question is likely to come up as one of the primary questions in software development or similar roles in an interview. It aims to test your understanding of the REST interface and its functions. To answer this question, consider explaining in detail the meaning and application of this interface from a software development perspective. Try giving examples to make your answer more specific.

Example: "REST stands for Representational State Transfer, and REST API is an application programming interface that follows the REST architectural style and allows various RESTful web services to interact with each other. Computer scientist Roy Fielding created this application interface. To fully understand REST API, it helps if you know the basics of API. An API is a programming interface that enables users to interact with a program through a client, any web browser. For example, when you use your browser to access a website, you are interacting with that website's API through the browser."

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What is the architectural style for web APIs in REST?

Employers ask this question to assess your basic understanding of the REST interface and whether you know its essential components. To answer this question, consider explaining the REST interface briefly before speaking about its architectural style.

Example: "REST is a set of constraints that software developers apply in an application to make it RESTful. The REST architecture contains a few essential characteristics, including HTTP, XML/JSON and an address. HTTP allows a client to communicate with the enterprise server. XML/JSON acts as a formatting language, and the address, a simple Uniform Resource Identifiers (URIs), helps to access the services and conduct stateless communication, which is a situation when the server doesn't rely on information from previous requests from the user."

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What is RESTful?

This question is likely to come up to assess your functional understanding of the architectural interface used in REST. Employers can also ask about this in combination with any of the two previous questions. To answer this, you can begin by briefly explaining what REST is and then describe the definition and essential functions of RESTful.

Example: "The software industry follows a set of guidelines to develop stateless, reliable and functional Web APIs. RESTful is one of the common APIs that developers use and that follows a design according to the constraints of REST. These RESTful web APIs use HTTP methods to access various URL-encoded parameters. These APIs can also use programming languages like JSON or XML to transmit data from one server to another. You can use RESTful to access a file's URL and determine the response it generates. For example, the resultant payload can tell if the resource has changed."

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How can you test REST API? What tools do you require?

When the interviewer asks you two specific questions such as this one, ensure that you answer them separately. This question is likely to assess your understanding of the testing methods used in REST API, along with essential tools that you can use to perform these tests. To answer this question, consider sharing your experience while testing the REST API using the STAR method of answering, as it can add more depth to your answer.

Example: "To test REST API, one can use specific software designed to assess RESTful constraints. Developers can choose from several popular tools depending on their individual and project requirements. Some of the commonly used tools for practical API testing include SoapUI, Katalon Studio and Postman.

As an API developer at Wellenough Mind Startup, my role was to test every API, and I used SoapUI because it was easy to download and access. I initially began with the free version to test its compatibility and functionality and later opted to use the product professionally. The results showed my applications to be constantly RESTful, which was good as a new developer, and it helped my team perform our tasks smoothly."

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What is the difference between REST and AJAX?

Interviewers ask this question to determine your understanding of two similar concepts and your ability to apply nuance and critical thinking while answering the questions. To answer this question, consider sharing the primary differences between these two subjects, followed by some information on various web development technologies or similar concepts such as Remote Procedure Call (RPC) and Message-oriented Middleware (MOM).

Example: "The major difference between REST and AJAX is that the request/response function is different between them. In REST, the request/response involves a URL structure and resources, whereas in AJAX, you transmit requests using XMLHttpRequest objects, and a response occurs when the JavaScript code changes the page. Also, REST is a software development interface, while AJAX is a set of web development resources. Another striking difference is that REST requires customers to interact with internal servers, but AJAX actively prevents it."

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What are the principal features of REST?

Interviewers can ask this fundamental yet technical question to test your foundational understanding of the REST interface. Employers want to assess your experience, skillset and functional knowledge of some of the essential components of REST that all software developers use. You can answer this question by describing each of the critical features of the programming interface clearly and briefly.

Example: "Some of the principal features of REST are that it enables a stateless form of communication and uses the GET function to access various resources. When applications are completely RESTful, the developers can restart the server between calls as data passes through it. Another important feature is that it supports JSON and XML languages and is simpler than SOAP. It also eases the work of developers by displaying error messages within the REST interface."

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What well-known HTTP methods does REST use?

The employers can ask you this question to test your technical and functional understanding of the REST interface. Since the question seeks to test your knowledge of the well-known methods, consider mentioning the popular methods regarding REST, apart from the ones you may have used.

Example: "There are various HTTP methods that REST uses to perform its functions comprehensively. Popular methods include GET, POST, PUT, DELETE, OPTION and HEAD. Out of these methods, the most used method is GET as it enables developers to access data for a specific resource using the REST API."

What are the benefits of using REST?

This question is fundamental to interviewers to assess your complete understanding of the REST interface. Knowing a particular programming interface means being well-aware and updated about its pros and cons. To answer this question, consider sharing your experiences using REST and discussing the benefits you have achieved for your organisation.

Example: "REST has many advantages. This programming interface is easy to scale, flexible and portable, and works independently from the client and server, making the development process much easier. In my job as an API developer for DazzlD, I built an API that securely provided user access to certain features and helped scale their website enormously. It was a massive success as the organisation is still using it today."

Please note that none of the companies mentioned in this article are affiliated with Indeed.

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