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Rest Services Interview Questions
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Last Updated: Jun 12, 2024

Rest Services Interview Questions

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Before proceeding with the Rest Services interview questions, let us understand first what is Rest. Roy Fielding, a computer scientist, defined REST.

A Restfulful web application introduces information about itself in the form of resource information. It also allows the client to perform actions on those resources, such as creating new resources (for example, creating a new user) or changing existing resources (i.e. editing a post). We will go through a lot of questions about rest services interview questions while going through this blog. 

To make your APIs Restful, you must adhere to a set of guidelines when creating them. The REST set of constraints will make your APIs relatively easy to use and discover, which means a developer who is just getting started with your APIs will have an easier time training how to use them.

Source: rest services interview questions


REST is an acronym that stands for REpresentational State Transfer.

When a Restful API is called, the server sends a representation of the state of the requested data to the client. Today, it is one of the most popular architectural styles for web services, microservices, and APIs. REST APIs are APIs that adhere to the REST architectural style.

We will also discuss web services. Web services are a well-known term when it comes to exchanging data across multiple applications or software. These services, which are based on the client-server model, can be used by multiple application software written in various languages and can run on a variety of platforms. Now let us see useful and important rest services interview questions. And make most of this topic.

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Rest Services Interview Questions


Let us now discuss the rest services interview questions.

1. What do you think about restful web services? Explain in detail.
RESTful web services are loosely coupled, lightweight web services that are ideal for creating APIs for clients spread across the internet. Representational State Transfer (REST) is a client-server application architectural style centered on the transfer of resource representations via requests and responses. Data and services are considered resources in the REST architectural style and are accessed via Uniform Resource Identifiers (URIs), which are typically links on the Web. Documents represent the resources, which are acted on using a set of simple, well-defined operations. 
A REST resource could be the current weather conditions in a city, for example. An XML document, an image file, or an HTML page could be used to represent that resource. A REST resource could be the current weather conditions in a city, for example. The REST architectural style is intended to employ a stateless communication protocol, most commonly HTTP. Clients and servers in the REST architecture style exchange resource representations via a standardized interface and protocol.


2. What are the characteristics of RESTful Web Services?
REST services have the following characteristics:

  • No condition: 
    REST Services can be resized to optimize performance in order to meet the demands of all potential clients. To minimize client response time, server farms with charge balance and failover or distinct server levels must be implemented.
  • Client-Server Relationship:
    Client-Server architecture is required for REST services. A server that contains the resources and conditions, as well as the clients who use them
  • Information that can be cached:
    Cache-enabled server responses should be used to improve network traffic efficiency. REST clients use this information to determine whether to perform a local copy of the resource, including the time and date of the request.
  • Reliable interface:
    The explicit use of HTTP (HyperText Transfer Protocol) methods is one of the key features of REST Web services.
  • Named resource access:
    A REST system is made up of resources that can be accessed via URL and must be intuitive, predictive, and simple to understand and configure. A hierarchical structure, similar to directories, is one way to accomplish this. It could be a distinct root node from which subdirectories are created to expose the main service areas until they form a tree containing resource information.
  • Additional resources:
    The server's resources are typically interconnected. As a result, a resource's condition information should grant permission to other resources.

Source: rest services interview questions

3. What exactly are HTTP Methods?
POST, GET, PUT, PATCH, and DELETE are the most commonly used HTTP methods. These methods correspond to the operations create, read, update, and delete (or CRUD). There are a few other methods, but they are used less frequently.

GET: The GET method is used to retrieve data from a server using a given URI. GET requests should only retrieve data and have no other effect on the data.

HEAD: The same as GET, but only the status line and header section are transferred.

POST: A POST request is used to send data to the server, such as customer information, file uploads, and so on, via HTML forms.

PUT: Replaces the uploaded content with all current representations of the target resource.

DELETE: Deletes all current representations of the resource specified by a URI.

Source: rest services interview questions

4. What is the distinction between PUT and POST?
A POST method is similar to a factory method. You add data to it to make what you want, and whatever is on the other end knows what to do with it. A PUT is used to update existing data at a given URL or to create something new when the URI is known but does not already exist (as opposed to a POST which will create something and return a URL to it if necessary).


5. What are the essential components of an HTTP request and response?

The following are the essential components of HTTP requests:

HTTP Version – This indicates the version.

Request Body – This is the message content.

Request Header – Contains metadata for the HTTP request message, such as cache settings and client type.

URI – Identifies the server's resource.

HTTP methods such as GET, POST, and PUT are indicated by the verb.


The following are the essential components of an HTTP response:

HTTP Version – The current version of HTTP.

Response Body – Represents the content of the response message.

Response Header – Metadata for the HTTP response message, such as content length and server length.

Status/Response Code – This code represents the server condition for the requested resource.


6. Please compare SOAP and REST.

→ SOAP tightly couples web services and clients. Furthermore, it establishes some strict guidelines. REST, on the other hand, does not adhere to too many standards while also allowing for loose coupling.

→ Data Format and Preference – REST is preferred here because it supports a variety of data formats, including HTML and JSON. SOAP only accepts the XML data format.

→ While SOAP is a standard protocol for creating web services, REST is an architectural style for creating web services.

→ JAX-RS is the Java API for RESTful Web Services, while JAX-WS is the Java API for SOAP Web Services.

→ REST requires less bandwidth and resources and exposes business logic through URIs. SOAP, on the other hand, requires more bandwidth and resources and exposes business logic through service interfaces.

→ Security: REST lacks a defined binding contract as well as its own security methods. SOAP, on the other hand, uses the WSDL contract to connect client programs and web services and has its own set of security protocols.


7. What points should be considered when developing a secure RESTful web service?

The following points should be considered while designing a secure restful web service.

→ Implement DELETE, GET, POST, PUT, and other methods with appropriate constraints.

→ Use the HTTP generic message whenever and wherever it is needed.

→ The POST method is used to send sensitive data, such as the username and session token password. Never use it via the URL.

→ Every time a request is made, perform user session-based authentication.

→ Protect the server from SQL injection attacks by validating all inputs.


8. What are the benefits and drawbacks of a REST API?

Benefits of REST API:

→ Because of its simplicity and well-known API, REST API is simple to understand and learn.

→ REST API allows you to organize complex applications and make it simple to use resources.

→ The high load can be handled with the assistance of an HTTP proxy server and cache.

→ REST API is simple to use and explore.

→ It makes it simple for new clients to work on other applications, whether they are purpose-built or not.

Source: rest services interview questions

REST disadvantages or challenges:

→ Inadequate state management: most web applications require stateful mechanisms.

→ Finally, unlike SOAP, REST does not impose security. That is why REST is appropriate for public URLs but not for private URLs.


9. What is the main difference between rest and restful?

The REST web service is a Representational State Transfer and an architectural structure for creating web services, whereas the RESTful service is one that implements that pattern. So there is no distinction between the two. However, how well your architecture meets your needs and grows with your business is more important than how well it meets an absolute standard.


10. What is the difference between AJAX and REST?

AJAX is an abbreviation for making asynchronous requests in JavaScript, which traditionally involves sending and receiving XML (although nowadays, JSON is often used instead of XML). So that's the approach you take on the client-side.

REST is a concept for HTTP request exchange, so you're creating RESTful request calls against the REST-API you implemented on the server-side.

Source: rest services interview questions

11. Describe the HTTP response status codes.

HTTP response status codes indicate whether or not a particular HTTP request was successfully completed. The responses are classified into five categories:

  1. Responses with information (100–199)
  2. Responses that were successful (200–299)
  3. Messages of redirection (300–399)
  4. Responses to client errors (400–499)
  5. Responses to server errors (500–599)
  6. HTTP status codes that are commonly used include:

200: successful request.

201: Entity or entities created as a result of a successful request

400: Invalid request. The client's request is invalid.

Unauthorized (401). The user is not authorized to access a resource and is therefore unauthenticated.

Forbidden (403): The user is not authorized to access a resource; however, the user is authenticated.

404: Page not found. The resource was not found.

500: Internal server error. Error on the generic server.


12. Explain the concept of statelessness in REST.

Because HTTP requests are statelessness, they occur in complete isolation. When a client sends an HTTP request, it includes all of the information required by the server to fulfill the request.

The server never uses information from previous client requests. If such information is required, the client will include it in the current request.


13. What is Microservice Architecture?

Microservices architecture, also known as microservices, is a design approach or style for developing applications. It entails breaking down large apps into smaller, functional units that can function and communicate independently.

The microservices architecture concentrates on categorizing otherwise large and bulky applications. Each microservice is designed to address a specific aspect and function of an application, such as logging, data search, and so on. Several of these microservices work together to form a single efficient application.

Source: rest services interview questions

14. What exactly do you mean when you say "idempotent operation"?

Idempotence is a property of some operations in programming and mathematics which means they produce the same result no matter how many times they are executed.

Idempotence can be a property of many different code elements in programming, including functions, methods, requests, and statements. Idempotence is a property that is language agnostic: it means the same thing in any operating context.


15. Describe the cache-control header.

Cache-control is an HTTP header used in both client requests and server responses to specify browser caching policies. Policies specify how a resource is cached, where it is cached, and how long it can be cached before it expires (i.e., time to live).

The cache-control header is composed of directives. The following is a brief description of the various cache-control headers:

Public: Public resources can be cached by any intermediate component between the client and the server.

Private: Only the client can cache resources that are marked as private.

No cache indicates that a specific resource cannot be cached and thus the entire process is halted.


16. What exactly is Payload?

Simply put, the payload is the body of the HTTP request and response message. It is optional and is determined by the HTTP method name, i.e. 

→ The HTTP request message without a body in the case of the GET HTTP method.

→ The HTTP request message with the body in the case of the POST HTTP method

In the HTTP request message, the 'Content-Type' header name is used to represent the payload format. For example, JSON, XML, and so on.


17. Describe the limitations of a uniform interface.

Uniform Interface: It is a key constraint that distinguishes a REST API from a non-REST API. It implies that regardless of device or application type, there should be a consistent way of interacting with a given server (website, mobile app).

The four Uniform Interface principles are as follows:

→ Individual resources are identified in requests that are resource-based. For instance, API/users.

→ Manipulation of Resources Using Representations: The client has a representation of the resource that contains enough information to modify or delete the resource on the server, assuming it has the necessary permissions. For example, when a user requests a list of users, he or she typically receives a user id and then uses that id to delete or modify that specific user.

→ Messages that are self-descriptive include enough data to describe how to process the message so that the server can easily analyze the request.

→ HATEOAS (Hypermedia as the Engine of Application State): It should include links for each response so that the client can easily find other resources.


18. What exactly is CRUD?

CRUD is an acronym used in computer programming that refers to the four functions required to implement a persistent storage application: create, read, update, and delete. Persistent storage is any data storage device that retains power after being turned off, such as a hard disc or a solid-state drive. Random-access memory and internal caching, on the other hand, are examples of volatile memory, as they contain data that will be erased when the device loses power.

19. What are the best techniques for creating a resource representation?

The following are critical considerations when designing a resource representation format in a RESTful web service:

→ Understandability Both the server and the client should be able to understand and use the resource's representation format.

→ Completeness A format should be able to completely represent a resource. A resource, for example, may contain another resource. The format should be able to represent both simple and complex resource structures.

→ A resource may be linked to another resource; a format should be able to handle such situations.


20. What is the API Gateway pattern?

An API Gateway is a good approach to consider when designing and building large or complex microservice-based applications with multiple client apps. This pattern is a server that serves as a single point of entry for specific groups of microservices. It is similar to the Facade pattern from object-oriented design, but it is used in a distributed system. The API Gateway pattern is also known as the "backend for frontend" (BFF) pattern because it is built with the needs of the client app in mind.

As a result, the API gateway acts as a bridge between the client apps and the microservices. It serves as a reverse proxy, directing client requests to services. It can also offer other cross-cutting features like

Source: rest services interview questions

21. What should the HEAD method of RESTful web services serve?

HEAD is a method-level annotation in REST that indicates that the following method will only respond to HTTP HEAD requests. It is used to obtain only the server's response status and header information ( entity ). The HEAD method can be used to determine whether a resource exists on the server by evaluating the status or header of the response, such as testing the validity of hyperlinks.

This method is identical to the GET method. The metadata in the HTTP header of a response to a HEAD method request is the same as the metadata in the HTTP header of a response to a GET method request. The only difference is that the response to a HEAD method request does not include the message body, whereas the response to a GET method request does.


22. What exactly is a postman? What is its purpose?

Postman is an API client that allows developers to easily create, share, test, and document APIs. This is accomplished by allowing users to create, save, and read simple and complex HTTP/s requests. As a result, work is more efficient and less tedious. When it comes to executing APIs, Postman is extremely useful. 'Collections' is one of Postman's fantastic features. 'Collections' enable you to group together several APIs that may be related or should be executed in a specific order.


Must Read Web Developer Interview Questions

23. Is it possible to implement transport layer security (TLS) in REST?

We certainly can. TLS encrypts the interaction between the REST client and the server and allows the server to be authenticated by the client. As the Secure Socket Layer's successor, it is used for secure communication (SSL). HTTPS is compatible with both TLS and SSL, making it useful for implementing RESTful web services. One thing to keep in mind is that the REST protocol inherits the properties of the protocol it implements. As a result, security measures are dependent on the REST protocol.


24. What is HTTP Basic Authentication?

HTTP Basic Authentication requires the server to request login details from the web client and then compare the user name and password to a database of authorized users. When basic authentication is declared, the following events take place:

→ A customer requests access to a restricted resource.

→ The web server displays a dialogue box in which the user name and password are requested.

→ The client sends the server the user name and password.

→ The server checks the validity in the specified realm and returns the requested resource if successful. 


25. In Spring, define RestTemplate.

RestTemplate is an HTTP client that runs in the background. It employs a straightforward template method API over underlying HTTP client libraries such as JDK HttpURLConnection, Apache HttpComponents, and others.

Since Spring 5.0, a new client WebClient has been available for creating both synchronous and asynchronous queries. RestTemplate will be deprecated in future releases in favor of WebClient.


26. Please explain your understanding of SOA.

SOA is an acronym that stands for Service Oriented Architecture. It is defined as a service-based architectural pattern. Through the communication protocol, application components in SOA provide services to other components.

The communication could include data exchange or some kind of service coordination activity. The following are key SOA principles:

→ The service contract, in addition to being standardized, must include the entire description of the services.

→ Services should be refillable in order to work with various application types.

→ Loose coupling refers to the lack of dependency between web services and clients.

→ Must adhere to the Service Abstraction rule, which states that the service should not expose how functionality is executed to the client application.


27. What do you mean by WSDL?

WSDL is an XML format for describing network services as a collection of endpoints that respond to messages containing either document-oriented or procedure-oriented data. To define an endpoint, the operations and messages are described abstractly and then bound to a concrete network protocol and message format. Abstract endpoints are formed by combining related concrete endpoints (services). However, the only bindings described in this document are about using WSDL in conjunction with SOAP 1.1, HTTP GET/POST, and MIME.

Source: rest services interview questions

28. What are the different components of WSDL documents?

→ Binding – Defines and determines the protocol and data format for each port type.

→ Message – Specifies the data elements for each operation. It could be the entire document or a previously unmapped argument.

→ Operations – Specifies the operations that must be carried out in order to process a message.

→ Port Type – Specifies the set of binding operations that can be performed.

→ Types – Describes the message data types used by web services in the form of XML schema.


29. What is the meaning of a web service protocol stack?

The web service protocol stack is made up of various protocols or procedures that are used to explore and execute various types of web services. It has four layers, which include the following. Service Discovery. Service Transport. Service Description. XML Messaging.


30. Is it necessary to have security in web services? Explain.

Web services require a high level of security. Neither the XML-RPC nor the SOAP specifications, however, make any explicit security or authentication requirements.

Web services have three distinct security issues.

Network Security, Authentication, Confidentiality

SSL, or Service Socket Layer, is used to secure web services, which aids in the creation of an Entrust Secure Transaction Platform.

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Frequently Asked Questions

What is the architectural style for developing web APIs?

The architectural styles for developing web APIs are as follows:

  • HTTP is used for client-server communication.
  • XML/JSON as a language for formatting
  • The address for the services is a simple URI.
  • Communication that is stateless

Mention the tools needed to test web API.

SOAPUI is a SOAP WS tool, and the Firefox "poster" plugin for RESTFUL services.

What tools or APIs are available for developing or testing web APIs?

Web service testing tools for REST APIs include Spring REST web service based on MVC, Jersey API, CXF, Axis, and Restlet.


To conclude this blog, firstly we discussed some basics about rest services and rest API. After that, we looked into many rest services interview questions. Some questions are discussed in every detail. This blog will really help you in understanding rest services interview questions. 

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