Top REST API Interview Questions and Answers

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As the popularity of REST (Representational State Transfer) API grows, the demand for skilled REST API developers also increases. If you're looking to hire developers with knowledge and experience in REST APIs, we've compiled a list of top REST Interview Questions and Answers to input into your process. In this article, we will cover the basics of REST, the principles of RESTful architecture, and common and advanced REST interview questions and answers.

Understanding REST API Basics

RESTful API has become a buzzword in the world of web development. It has become the go-to choice for developers who want to build scalable and maintainable web services. REST is an architectural style that defines a set of constraints that must be followed while creating web services. The primary goal of REST is to create a scalable and maintainable web service.

What is REST?

REST stands for Representational State Transfer. It is an architectural style for designing networked applications. REST is based on the HTTP protocol, which is used to transfer data between the client and the server. RESTful API is an implementation of REST architecture.

REST is based on a few principles that help in building web services that are easy to maintain, scalable, and can be consumed by various clients. These principles are:

Principles of RESTful Architecture

  • Client-server architecture: In REST, the client and server are separated, and they communicate through HTTP requests and responses.
  • Statelessness: RESTful API does not store any client context on the server. Each request from the client contains all the necessary information to complete the request.
  • Cacheability: RESTful API responses can be cached, which improves the performance of the web service.
  • Layered system: RESTful API can be built on top of other web services, which makes it a layered system.
  • Uniform interface: RESTful API has a uniform interface, which makes it easy to understand and use.

Difference between REST and SOAP

SOAP (Simple Object Access Protocol) is an XML-based messaging protocol, while REST is an architectural style. SOAP uses XML to define the message format, and REST uses plain text or JSON format. SOAP is considered more robust, while REST is lightweight and more accessible.

SOAP is used in enterprise-level applications, where security and reliability are of utmost importance. RESTful API, on the other hand, is used in web applications that require scalability and maintainability.

In conclusion, RESTful API has become the preferred choice for developers who want to build scalable and maintainable web services. Its principles make it easy to understand and use, and it can be consumed by various clients.

Common REST Interview Questions

RESTful APIs have become increasingly popular due to their simplicity and scalability. They are used by many companies to provide access to their resources over the internet. If you are planning to interview for a position that requires knowledge of REST, you should be prepared to answer some common questions. Here are a few:

What are the HTTP methods used in REST?

HTTP methods are used to perform operations on resources. RESTful APIs use the following HTTP methods:

  • GET: Used to retrieve data from the server.
  • POST: Used to create a new resource.
  • PUT: Used to update an existing resource.
  • DELETE: Used to remove a resource.

These HTTP methods are used to manipulate resources in a RESTful API.

Explain the concept of statelessness in REST

Statelessness is a fundamental concept in REST. It means that the server does not retain any information about the client's state. Each request sent to the server must include all the necessary information to process the request. This approach makes the RESTful API scalable and easy to maintain.

Statelessness is achieved by using HTTP methods and status codes to communicate between the client and the server. The client sends a request to the server, and the server sends a response back to the client. The response contains the necessary information to complete the request.

What is a resource in REST

A resource is a logical representation of an object or an entity. Resources are identified via a unique identifier, which is called a Uniform Resource Identifier (URI). For example, a resource could be a user, a product, or an order.

Resources are the building blocks of a RESTful API. They are the objects that the client interacts with. Each resource has a unique URI, which is used to identify it.

How does caching work in REST?

RESTful APIs use caching to reduce the number of requests sent to the server and improve performance. The server includes a Cache-Control header in the response to specify how long the client can cache the response. The client can then use the cached response for subsequent requests.

Caching is an essential feature of RESTful APIs. It allows the client to reduce the number of requests sent to the server and improve performance. Caching is particularly useful for resources that do not change frequently.

What are the best practices for designing RESTful APIs?

The best practices for designing RESTful APIs are:

  • Use nouns to represent resources.
  • Use HTTP methods correctly.
  • Use versioning to manage API changes.
  • Provide clear documentation.
  • Use security measures such as authentication and encryption.

Following these best practices will ensure that your RESTful API is easy to use, scalable, and secure.

Advanced REST Interview Questions

As RESTful APIs continue to gain popularity, it is important for developers to have a strong understanding of the architecture and best practices. Here are some advanced REST interview questions that can help you assess a candidate's knowledge.

How to handle errors in RESTful APIs?

Handling errors in RESTful APIs is critical to providing a good user experience. When an error occurs, the API should return an appropriate HTTP status code to indicate the success or failure of a request. For example, a 200 status code indicates success, while a 404 status code indicates that the requested resource was not found.

In addition to the status code, the server can include additional information about the error in the response body. This can include a message describing the error, as well as any relevant details such as a stack trace or error code. It is also recommended to use standardized error codes, such as HTTP error codes or application-specific error codes, to make it easier for developers to understand and handle errors.

What is HATEOAS and why is it important?

HATEOAS (Hypermedia as the Engine of Application State) is a constraint of the RESTful architecture that states that the API should provide links to related resources along with the response. This approach makes the API self-descriptive and allows clients to navigate the resource hierarchy without prior knowledge of the API.

For example, if a client requests a list of products from an e-commerce API, the API might include links to each individual product, as well as links to related resources such as categories, reviews, and recommendations. This allows the client to easily explore the available resources and discover new functionality without needing to consult external documentation.

How to secure RESTful APIs?

Security is a critical consideration when building RESTful APIs, especially for applications that handle sensitive data or perform critical operations. There are several best practices that can be used to ensure that RESTful APIs are secure.

First, RESTful APIs should use authentication and authorization mechanisms to ensure that only authorized users can access the resources. This can be done using standard protocols such as OAuth or JSON Web Tokens (JWTs).

Second, SSL/TLS encryption should be used to protect sensitive data transmitted over the network. This ensures that data cannot be intercepted or tampered with by attackers.

Finally, it is recommended to use input validation and avoid storing sensitive data in plain text. This can help prevent common attacks such as SQL injection and cross-site scripting (XSS).

What is the role of versioning in RESTful APIs?

Versioning is used to manage changes in the API over time. As APIs evolve, new features may be added, existing features may be modified, and old features may be removed. Versioning allows clients to access different versions of the API simultaneously without affecting the existing clients.

There are several approaches to versioning in RESTful APIs. One common approach is to include a version number in the resource URI (e.g. /api/v1/products). Another approach is to use HTTP headers to specify the version (e.g. Accept: application/vnd.myapi.v1+json). Finally, some APIs use media types to indicate the version (e.g. application/vnd.myapi.v1+json).

How to handle pagination in RESTful APIs?

When dealing with a large dataset, it is recommended to use pagination to reduce the amount of data transferred over the network. Pagination allows the client to request a subset of the data, rather than the entire dataset.

The server can include information about the total number of pages and the current page in the response. This can be done using HTTP headers or by including the information in the response body. The client can then use this information to navigate between pages.

For example, a client might request the first 10 products in a list by sending a GET request to /api/products?limit=10&page=1. The server would respond with the first 10 products, as well as information about the total number of pages and the current page.

Pagination is an important technique for improving the performance of RESTful APIs, especially when dealing with large datasets.


These are some of the top REST interview questions and answers to help you prepare for your next interview. It is essential to have a good understanding of REST basics, principles, and best practices. In addition, a candidate who is familiar with advanced topics such as error handling, security, versioning, and pagination will stand out.