Top 15 REST API Interview Q&A

Building web APIs, microservices, and other web services have become one of the basic business needs nowadays. And one of the most popular approaches to it is to use REST APIs. Of course, you can build some top-notch quality software using the best programming languages but when you are offering services, you are offering a package of such software applications or features built using a different programming language that works in sync to fulfill the requirements of the users. 

And to integrate this software, you have to use the REST API. of course you already know all of this. But delivering the same information when asked for or showing how it all works can be a little tough. And that’s why many developers tend to fail the interview. Although they are skilled enough, they don’t know what questions are going to be asked of them. Also, even if you know the answers, you are not sure about how to convey them.

REST API Interview Questions

1. What is a REST Resource?

A REST resource is a collection of resources that expose a defined set of operations (or methods) on an entity. The resources can be anything. They are usually organized into hierarchies, where each hierarchy represents an object with the same root and different “child” objects. These hierarchies are called “resources” in REST terminology because they represent items that may be accessed and manipulated by clients, such as web browsers or mobile app developers.

2. What are the features of RESTful Web Services?

The following are the features of RESTful Web Services:

• It is a uniform interface for accessing resources.
• A resource has properties and methods which can be identified by their names and definitions respectively.
• Support for Uniform Access to Resources Over Distributed Networks
• Hypertext-style Linking Using URLs (Uniform Resource Locators) between Resources
• Use of Hypertext Transfer Protocol (HTTP) for Inter-Resource Communication
• Separation of Concerns in Data Modeling – Use URIs to Represent Resources, Not Forms or RDFS Statements
• The representations that are sent in response to a request can be in various formats and media types such as text/plain, application/XML, or any other format or media type.
• The representation must be valid according to the HTTP protocol and syntax rules.
• The representation must be cacheable and include appropriate header information so that the user agent may use it when revalidating subsequent requests on the same resource.

3. What is the concept of statelessness in REST?

RESTful web services are defined as being stateless. They do not require any state to be saved between requests. Also, to function properly, they don’t need any data related to the client  This allows for a very lightweight and fast response time, which is important for mobile devices.

4. What are the HTTP Methods?

HTTP methods are the ways that you can send information from your web server to your application. There are many methods but the most popular ones include GET, POST, PUT and DELETE. 

GET requests to send a representation of some data back to the client or browser. This is what we mean by “GET”. POST requests do not return data; they create something on the server side and then return it as an entity. This is what we mean by “POST”. 

PUT requests are similar to POST requests in that they create something on the server side, but they allow you to modify an existing resource on the server side. This is what we mean by “PUT”. DELETE is used to delete something from the server.

5. What are HTTP Status codes?

Every HTTP request has been allocated status and a way of determining that status is called HTTP status codes. They are returned in the response header field, but they can also be used in other places. 

The most common HTTP status code is 2xx (indicating success), although this is not necessarily true for every case. For example, a 400 Error Code means that something went wrong on your server, while a 404 means that there was nothing at all on the page you requested. 

6. What do you understand about JAX-RS?

JAX-RS is a standard for building Java web services that can be used in multiple programming languages. It’s not just for Java, but also for JavaScript and other languages that run on the server.

JAX-RS defines a set of annotations that you can use to tag your classes and methods with information about how they should be invoked, how they should be marshaled to/from the request/response, and other details. These annotations are called JAX-RS annotations.

One of the main goals of JRS is to enable easy integration of existing Java EE applications with third-party libraries written in other languages like Javascript or Ruby.

7. What is URI?

A string of characters that identifies the resource on the web uniquely is known as URI. A URI can be thought of as a hyperlink, which points to some other resource on the internet. For example, in this article, http://www.example.com/search?q=computer is a URI that instructs browsers and search engines what web page you want to go to when you click on it.

A URI has three parts:

The scheme (e.g., “HTTP”) tells the browser how to interpret this URL. In this case, “HTTP” means that the browser should use HTTP (Hypertext Transfer Protocol) to request information from this server.

The hostname (e.g., “example.com”) provides information about the location of the server or domain where the resource lives (in this case).

The path (e.g., “/search”) tells the browser where in the directory hierarchy of this site you want it to look for this file (in this case).

8. What makes REST services to be easily scalable?

REST services are easy to scale because they don’t require complex software. The HTTP is just a simple request & response model which can be easily implemented in any system and application. It’s also very flexible, allowing custom headers, response codes, and bodies.

A REST service can be deployed on any server or cloud platform that supports the HTTP protocol. A REST service doesn’t need to be built from scratch; it can use existing code as long as it conforms to standards such as JSON and XML. REST services also have a very small footprint as there is no middleware layer added to them. 

The advantage of using REST services is that it allows developers to focus on building their applications without having to worry about scaling issues.

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