REST Interview Questions & Answers

REST Interview Questions & AnswersREST, short for representational state transfer, is an architectural style used to design networked applications. It follows a stateless, client-server protocol, commonly utilizing HTTP. While SOAP was previously popular for implementing web service APIs, REST has gained significant preference among programmers due to its straightforwardness and scalability.
RESTful APIs have led to the emergence of trends like cloud computing and microservices-based architecture. They have simplified communication and computing over the Internet, making it essential for developers to understand REST, its workings, features, and secure service development in line with this trend. Many companies value developers with REST knowledge as they can help create scalable, easily maintainable products that can reach a global audience through the Internet.
So, if you are ready to make a career in development, prepare top REST Interview Questions about REST. Gaining a fundamental knowledge of REST APIs, their benefits, best practices, and their importance is critical to tackling the technical interview questions and answers asked during developer interviews.

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REST refers to a web standards-based architecture that uses HTTP Protocol for data communication. It revolves over a resource where each component is a resource & the resource is accessed through a common interface using HTTP standard methods. REST was first developed in 2000 by Roy Fielding. It uses various representations to denote a resource such as JSON, text, & XML. In the REST architecture, a REST Server provides access to resources while a REST client accesses & presents the resources. Global IDs or URIs identify each resource in REST.

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Restful Web Services refers to a scalable, maintainable & lightweight service built on the REST architecture. It exposes API from an application into a uniform, stateless, & secure manner to the calling client.

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A web service refers to a collection of standards & open protocols used for exchanging data between systems & applications. Apps written in different programming languages & running on diverse platforms can use web services to exchange data across computer networks such as the Internet, similar to inter-process communication on a single computer.

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GET: It only provides read-only access to the resource.

POST: It submits info to the service for processing & usually returns to a new or modified resource.

PUT: It updates the resource at the request URL.

DELETE: It removes or omits the resource.

OPTIONS: It indicates techniques that are supported.

HEAD: It returns the meta-information

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A resource is a core element of the RESTful design. REST architecture treats all its content as a resource; it includes Images, Html Pages, Videos, Text Files, etc. The REST server provides access to resources where the REST client is used for modifying & accessing the resources. All its resources get identified through URI or Uniform Resource Identifier.

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AJAX REST
The requests are sent to a server using XMLHttpRequest The response is used by the JavaScript code to alter the current page. REST needs interaction between the customer & the server.
Ajax implies a set of technology & a technique of dynamically updating UI parts without needing to reload the page. REST has a URL structure & a request/response pattern that revolves around the use of resources.
Ajax removes interaction between the customer & server asynchronously. REST requires interactions between the customer & the server.

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The following are the main features of REST:

Client-server

  • REST’s client-server separation of concerns streamlines component implementation. It reduces the complexity of connector semantics, improves the effectiveness of performance tuning, & boosts the scalability of pure server components.
  • REST allows intermediate processing by restraining messages to be self-descriptive: interaction is stateless between the standard methods, requests, and media used to indicate semantics, exchange information, and responses explicitly indicate cacheability.

Statelessness

  • As per the REST architecture, the server doesn’t store a state about the client session on a server-side. This restriction is known as Statelessness.
  • Each request from a client to the server must contain all information required to understand the request & cannot leverage any stored context. Session state is thus kept entirely on the client.
  • The client is responsible for handling & storing all application state-related info on the client-side.

Caching REST API Response

  • Caching can store copies of frequently accessed data in various places along with a request-response path. When a consumer requests the resource representation, the request goes through a cache or a series of caches to the service hosting a resource.
  • If any cache along the request path has a fresh copy of the requested representation, it uses that copy to satiate the request. If no caches can satisfy the request, the request travels to the service.
  • Less interaction results in greater efficiency & scalability.

Layered system

  • A client cannot tell if it is connected to the intermediary or an end server. The intermediary servers can improve the system’s scalability through shared caches & load balancing.
  • Layered system constraints gateways, firewalls, & intermediaries’ proxies to be introduced at different points in communication without changing interfaces between components, thus enabling them to assist in communication translation or improve performance through large-scale shared caching.

Uniform Resources

  • All resources are accessed through a uniform interface.
  • Resources can be named through URL.

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The different integration styles are as follows:

  • Directly sharing or accessing the database.
  • Batch file-sharing or transfer.
  • Invoking remote procedure.
  • Swapping asynchronous messages over the message-oriented middleware (MOM).

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  • PUT is called to modify a resource, while the POST method is called to add a child resource.
  • PUT method responses can be cached, but one cannot cache the POST method responses.
  • You can use the UPDATE query in the PUT method, whereas you can use the create query in the POST method.
  • In the PUT method, the client decides the URI resource, but in the POST method, the server decides the URI resource. POST work as abstract, while PUT works as specific.
  • If you send the same PUT request many times, the result will always remain the same, but if you send same POST request many times, you will get different results.
  • POST method is not idempotent, but the PUT method is idempotent.

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Here are a few differences between RPC & Document style web services:

RPC Style

  • It uses parameters & method name to generate XML structure.
  • In RPC style, it is difficult to validate the generated WSDL against the schema.
  • The SOAP message is sent as many elements & keeps the operation name in RPC style.
  • The RPC style message is coupled tightly.
  • The parameters are sent as discrete values in this style.

Document Style

  • It can be easily validated against the predefined schema.
  • The SOAP message is sent as a single document in the Document style.
  • Document style message is coupled loosely.
  • SOAP message loses the operation name in the Document style.
  • Parameters are sent in XML format in this style.

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Both JAX-WS & JAX-RS are API libraries for doing communication in different ways in Java. JAX-WS is a library used to do SOAP communication in Java, while JAX-RS helps you do the REST communication in Java.

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Below are some testing tools for web REST APIs:

  • RapidAPI-It is the best API testing tool that has the largest API marketplace. Over a million developers use RapidAPI to test, find, & connect thousands of APIs with a single account. You can collaborate on APIs using RapidAPI for teams with internal & external APIs. Developers also use RapidAPI Testing on their internal APIs with RapidAPI Hub or RapidAPI Teams.
  • REST-assured– It is one of the best testing tools for APIs in Java. Rest-assured has a Java Domain-specific language & is an open-source tool. It eliminates the need for an expert in HTTP to test web APIs.
  • Postman– Postman is a scalable API testing tool that enables users to easily share knowledge with the team. It makes it easy for developers to share, test, document, & create APIs.
  • Paw– Paw is another potent API testing tool designed for Mac. It helps you to inspect a server’s response, generate client code, & build HTTP requests.
  • SoapUI– SoapUI is an on-premise API testing tool that enables developers to test SOAP, REST, Web Services, & GraphQL. SoapUI provides a robust solution to run, create, & analyze complex tests on web services. It boasts several unique features such as SOAP API testing, test reports, etc.
  • Katalon Studio– It is also a free API testing tool used for desktop, API, web, & mobile applications. Katalon Studio provides easy development by including all plugins & frameworks in a package. It is best suited for both experts & beginners with the Scripting & Manual modes.

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SOAP REST
SOAP refers to a protocol that enables the communication between two computers by sharing XML documents. Rest refers to a standard architecture for network-based software architectures.
SOAP only permits XML data. REST supports a diverse set of data formats.
SOAP reads cannot be cached REST-based reads can be cached.
SOAP is just like a custom desktop application, closely connected to the server. REST is more like a browser; it knows how to standardize methods & applications have to fit inside it.
SOAP is slower than the REST architecture. REST is faster than SOAP.
SOAP runs on HTTP yet envelopes the message. REST deploys the HTTP headers to hold meta information.

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Web services based on the REST Architecture are called RESTful web services. Such web services use HTTP methods to implement the REST architecture concept. It defines Uniform Resource Identifier or URI & provides resource representation like a set of HTTP & JSON Methods.

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There are various types of representations in REST such as JSON, XML, text-based, etc. However, JSON & XML are the most popular representing resources in REST. REST does not impose any restriction to use a particular format in representing resources. It mainly depends on the choice of developer & project. Thus, you can use any representing format to represent a resource in REST.

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When a client sends a message in the form of an HTTP Request & the server then responds in the form of an HTTP Response, it is called messaging technique. These messages contain metadata & message data which includes the information about the message itself.

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HTTP Requests mainly have five key elements, which are as follows:

  • Verb that indicates the HTTP methods such as PUT, GET, DELETE, POST.
  • URI (Uniform Resource Identifier) that identifies resources on the server.
  • HTTP Version that showcases the HTTP version (HTTP v1.1).
  • Request Header carries metadata as the key-value pairs for an HTTP Request message. Metadata can be a browser or client type; the client supports a message body format & cache setting.
  • Request Body indicates the content of a message or resource representation.

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  • Each HTTP response includes four key elements:
  • Status/Response Code: Indicates Server status for the resource present in the HTTP request. For example, 404 means resource is not found, and 200 means response is ok.
  • HTTP Version: Indicates HTTP version, for example-HTTP v1.1.
  • Response Header: Contains metadata for the HTTP response message stored in the form of key-value pairs. For example, content length, content type, response date, and server type.
  • Response Body – Indicates response message content or resource representation.

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Addressing locates resources present on the server to host web services. It is usually done with Unified Resource Identifier or URI.

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A URI or Uniform Resource Identifier is a string comprising characters that identify a logical or physical resource. URI follows syntax rules to ensure uniformity. It also maintains extensibility through a hierarchical naming scheme. Each resource in a REST architecture is identified by its URI.