The development of REST has made APIs quite accessible while also bringing out their true power and potential. With a resource-oriented architecture, REST APIs are simple to develop and as easily cacheable. And over the years, RESTful APIs have also started other crucial trends, such as microservice-based architecture and cloud computing. Therefore, it is no wonder that REST API developers are in demand in the current times given how they provide a competitive edge to companies that use RESTful services. If you aspire to work in the area of REST API development, here are some of the most common REST API interview questions that will prepare you for interviews at various companies. 

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Top REST API Interview Questions and Answers

1. What do you mean by RESTful web services?

REST is the common acronym used for Representational State Transfer, and it makes use of HTTP protocol for its implementations. Services that follow the REST architecture are known as REST web services. REStful services are popular for various features, such as being lightweight, scalability, communication support across various applications, and maintainability. 

2. What are the features of RESTful web services?

Following are the features that are a part of every RESTFUL service-

  • RESTful services follow the client-server model.
  • RESTful services leverage HTTP protocol when executing queries, fetching resources and data, and other functions. 
  • RESTful services maintain communication between the client and the server, and this medium of communication is called “messaging”. 
  • URIs make different resources accessible to the service. 
  • When there are repeated requests, the concept of caching helps minimize serve calls for the same requests.
  • RESTful web services also make use of SOAP services, which serves as an implementation protocol to the architectural pattern of REST.

3. What is a REST resource?

Like objects are considered resources in the object-oriented programming framework, each content in the REST architecture represents a resource. These resources are represented in various ways, such as images, text files, HTML pages, and other dynamic data. Each resource is globally identified using a URI, and these resources are accessible via the REST server, which are consumed and are open to modifications by the REST client.

4. What do you mean by statelessness in REST?

The REST architecture features a design that does not maintain the client state on the server, which is known as statelessness. The client’s requests are processed by the server when the client provides context, and the server identifies sessions when the client sends session identifiers. 

5. What are cache-control headers?

Cache-control headers are used for controlling caching and attaining caching ability. There are a few commonly used cache-control headers, which are as follows-

  • Public - Resources that are marked as public are open to being cached by either component between the client and the server.
  • Private - Since these resources are marked to be private, they are allowed to be cached only by the client. 
  • No-Store - When resources are marked as no-store, the responses can only be cached when the data is pulled from the client. Such responses cannot be cached by browsers. This type of cache control is useful when dealing with sensitive data, such as payment-related information and passwords. 

6. What are the disadvantages of RESTful web services?

Here are the disadvantages of RESTful web services-

  • One of the issues with REST web services is that it is impossible to maintain sessions as the concept of statelessness applies to these services. 
  • REST does not have inherent security restrictions. Since the security measures of the protocols that implement REST are inherited by it, one must be careful about implementing security measures, such as authentications based on TLS/SLS. 

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7. What is the definition of messaging in terms of RESTful web services?

Messaging is a technique used in REST which involves sending messages in the form of an HTTP request from the REST client to the server, and the server providing a response to that message in the form of an HTTP request. 

8. Explain ‘Addressing’ in RESTful web services.

Addressing is a process that involves locating resources on a REST server. The process of addressing these resources in the RESTful web services happens using a URL. This basically means resources have URLs, and URLs can be used to address single or even multiple resources. 

9. Why are REST services easily scalable?

One of the reasons why REST services are known to be easily scalable is because they follow the concept of statelessness. This means there is no data that is stored across requests on the server. Because of the concept of statelessness, the servers don’t require much communication when serving requests, which makes it easier for horizontal scaling.

10. What are Idempotent methods?

Methods that return the same outcome even when the same request has been made multiple times are known as Idempotent methods. This is a very crucial method that helps keep a check on the outcomes when the client-side sends various duplicate requests. When you use Idempotent, you can effectively avoid such errors.

11. How can RESTful web services be tested?

There are various tools that can help with the testing of RESTful web services, such as Swagger and Postman. The latter is loaded with several features that allow users to inspect request parameters, such as query parameters and headers as well as response headers. You can also use Postman to send requests to endpoints and display the responses. And these responses can be converted to XML and JSON. Swagger offers features very similar to that of Postman. However, with Swagger, you can also avail features, such as documentation of the endpoints.

12. What are payloads in RESTful web services?

Payload is the request data that is found in every HTTP request message’s body. However, payloads are only passed through the POST method, and they are not synonymous with request parameters. 

13. What is the maximum payload size that can be sent in POST methods?

While there are no restrictions placed on the size of the payload that can be sent in POST methods when speaking theoretically, it helps to remember that when payload size increases, it leads to a larger bandwidth consumption, and it also takes more time for the request to be processed. Therefore, payloads that are larger in size can impact the server performance. 

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Frequently Asked Questions

1. How do I prepare for a REST API interview?

In addition to knowing how to design a REST API, it  helps to know about the common REST API interview questions that companies generally ask. You should also know why companies prefer REST API and uses of REST API to be better prepared for a REST API interview.

2. What is the REST API used for?

In the REST API architecture, HTTP requests are used for accessing and using data. The data accessed using REST API can be used to read, update, delete, and create operations concerning resources.

3. What is the difference between API and REST API?

An Application Programming Interface entails rules used to define how different devices or applications communicate with each other and connect to each other. A REST API follows the principles of the REST architectural pattern to create web services. 

4. What is the full-form of REST API?

REST API is the acronym used for Representational State Transfer Application Program Interface. 

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Now that you have a fair bit of idea on how to answer some of the common REST API interview questions, you can now go ahead and answer the interviews with confidence. To upskill further and develop your software development skills, we would highly recommend Simplilearn’s Post Graduate Program in Full Stack Web Development. This program is designed in collaboration with Caltech CTME can help you develop and master some of the key software development skills.

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