Rest API Interview Questions

A REST API, commonly referred to as a RESTful API, is a web API that complies with the restrictions of the REST architectural style and enables communication with RESTful web services. Computer scientist Roy Fielding came up with the acronym REST, which stands for neural style transfer.

An API must meet the following requirements in order to be deemed RESTful:

• An HTTP-based client-server architecture consisting of clients, servers, and resources.
• Stateless client-server communication means that each request is distinct from the others and that no client data is stored between get requests.
• Data that can be cached to speed up client-server communications.
• A consistent interface between components to ensure the delivery of information in a standard format. This demands that:
• The resources requested are distinguishable from the client's representations.
• The representation that the client receives has sufficient information to allow for resource manipulation by the client.
• The information contained in self-descriptive messages sent back to the client is sufficient to specify how the client should handle them.
• After accessing a resource, a client ought to be able to use hyperlinks to locate all other presently offered activities they can perform because hypertext/hypermedia is available.
• Each sort of server, those in charge of security, load-balancing, etc. is organized using a layered approach that involves retrieving requested data invisible to the client hierarchies.
• Code-on-demand is an optional feature that allows the server to provide the client executable code upon request, enhancing client capability.

For easier understanding, we have divided these questions into two categories which are:

• Fresher
• Experienced
• FAQ's

Top 10 Frequently Asked Rest API Interview Questions

1. REST API: What is it?
2. Describe REST
3. What characteristics distinguish RESTful web services?
4. What markup language are used to describe the resources in REST APIs?
5. Distinguish between POST and PUT techniques.
6. How are REST APIs kept secure?
7. Important components of the construction of RESTful web services.
8. What are a few REST's flaws?
9. Mention a few of REST's most important attributes.
10. What does RESTful Webservices' statelessness entail?

Top REST API interview questions for freshers

1. What do RESTful web services' payloads entail?

In RESTful web services, payloads are the request data sent via the POST or GET technique and located in the message's body of an HTTP request.

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2. How big of a payload can you send using POST methods?

There isn't, theoretically, a cap on the size of the payload that can be transmitted via POST methods. Larger payloads, however, may require more bandwidth. As a result, processing the request by the server can take longer.

3. Which protocols are used by REST APIs?

REST APIs employ the HTTP protocol for client communication, whereas other protocols are used elsewhere.

4. What markup language are used to describe the resources in REST APIs?

Extensible Markup Language (XML) and JSON are used to represent the resources in REST APIs or JavaScript Object Notation.

Related Article: HTML vs XML

5. Distinguish between POST and PUT techniques.

POST Approach

• On the server, a resource can be created with POST.
• POST lacks idempotence.
• Responses from POST are cacheable.

PUT Approach

• A resource at a certain URI can be changed to another resource using the PUT command.
• PUT is idempotent, meaning that no matter how many times it is called, only one resource will be produced.
• Responses from PUT are not.

6. What does the REST API's caching do?

In order to quickly obtain a server answer in the future, REST API maintains a copy of the response in a specific region of computer memory. Catching is the term for this brief technique.

7. What is a practical illustration of a REST API?

• Weather apps use public REST APIs to communicate related data and display weather information.
• Airlines use APIs to disclose flight information to ticketing and travel websites for commercial usage.
• APIs are used by public transit providers to publish their data online and make it instantly accessible to mapping and navigation apps.

8.RESTful web services' drawbacks

• Because the client side does not supply a specific session id for it, RESTful web services are transient and do not keep session simulation responsibility.
• Inherently, REST is unable to enforce the security limitation. However, by putting protocols in place, it inherits them. To improve the security of the REST APIs, SSL/TLS authentication integration must be done with great care.

9. How are REST APIs kept secure?

Sensitive information such as user id, password, or verification token should not be visible in URIs. REST APIs can be kept secure with the help of security initiatives including such authorization and authorization, API server affirmation, TLs/SSL encryption, rate-limiting for DDoS attacks, and more.

10. What do REST API "Options" mean?

It is an HTTP protocol used to retrieve the HTTP operations or options that are supported and assist clients in selecting choices in REST APIs. CORS, or Cross-Origin Resource Sharing, employs the REST option approach.

11. How do you create a representation of resources for RESTful web services?

• Both the client and the server should have no trouble understanding it.
• Regardless of the layout of the format, it should be comprehensive.
• It should take into account how the resources are connected to one another and handle them carefully.

12. Important components of the construction of RESTful web services.

• Resources
• Demand 
• Headers
• Status codes
• Request Body
• Response Body

13. What distinguishes REST and SOAP from one another?

REST(Representational State Transfer) 

• It is a web service development architectural design pattern.
• It is more cacheable and speedier in speed.
• It just takes on the protocol-specific security measures that have been put in place.

SOAP (Simple Object Access Protocol) 

• It is a stringent protocol that is used to provide safe APIs.\
• It is not cacheable and moves more slowly.
• It can specify its own security precautions.

14. Describe the architectural design used to provide web APIs.

The architectural design used to create web APIs is

• Client-server communication via HTTP
• As a formatting language, XML/JSON
• Simple URI is used as the services' address.
• Stateless interaction

15. Describe the resources found in a REST architecture.

Logical URLs are used to identify resources; this is the fundamental component of a RESTful design. In contrast to SOAP web services, REST allows you to view the product information as a resource that should include all the necessary data.

Related Article: REST API Tutorial

16. Describe the various application integration styles.

The many integration patterns include

• Common database
• File transfers in batches
• remote procedure execution (RPC)
• Switching between asynchronous and message-oriented middleware (MOM)

17. Explain the distinction between RPC and document-style web services. How do you decide which one to pick?

In contrast to RPC-style web services, document-style web services allow us to send an XML document as part of a SOAP request. The application where a document-style web service is most suitable is one where an XML message behaves like a document, the content of which is subject to change, and the purpose of the web service is independent of the contents of XML messages.

18. Describe what JAX-WS and JAX-RS are.

Both JAX-WS and JAX-RS are frameworks (APIs) that allow for different types of communication in Java. A library called JAX-WS can then be used to do SOAP communications in Java, whereas JAX-RS enables REST communication.

19. List the resources or APIs available for creating or testing web APIs?

There are various web service testing tools for REST APIs.

• MVC Jersey API
• Spring REST web service
• CXF Axis 
• Restlet

20. A URI is what?

Unified resource identifier is referred to as a URI. A URI in REST is a string which designates a web server's resource. Each resource has a distinct URI that, when used in a Http response, enables clients to target it and do actions on it. Addressing is the process of directing traffic to a resource using its URI.

Top Rest API interview questions for experienced

21. Describe payload.

In GET or POST requests, the term "payload" refers to data in the content of the HTTP response and/or response messages. For instance, if you ask the Twitter API for a specific tweet, the payload will include the document detailing the tweet's content as well as any necessary files for putting the tweet on a website. The HTTP request's payload could also be included using the POST method. The tweet text that you supply in the POST request is the payload when you want to post a tweet using Twitter's API.

22. What are a few REST's flaws?

Statelessness is an advantage of REST, but it can also be a drawback. State is not preserved through REST. In those other words, the server doesn't save a history of previous communications. If maintaining state is required, the client is responsible for doing so. Developers must exercise caution and only use APIs from reliable, authentic providers as REST has less stringent security controls than SOAP. REST is therefore a bad choice for transmitting private data among servers and clients.

23. How are APIs tested?

RESTful APIs can be tested using a variety of software tools, including JMeter, Katalon and PostmanStudio. Sending numerous calls from the testing tool and watching how your API reacts are often steps in the testing process. You can quickly run numerous different scenarios thanks to the capability for automated testing provided by various testing solutions.

24. Mention a few of REST's most important attributes.

REST has a number of important features, including

• Because REST is stateless, the SERVER has had no state or session data
• The server might be resumed in between calls thanks to a well-implemented REST API because all data is sent to the server.
• While REST uses GET to access services, web services often employ POST to carry out tasks.

25. What is a resource in a restful web service?

The core idea behind Restful architecture is resource. A resource is a thing that:

• a kind, connection to other resources, and techniques that use it.

Resources are labeled as:

• their URI, the HTTP methods they accept, the type of data in the request and response, and the data format.

26. How does the architecture for microservices operate?

• Clients: Requests are sent by numerous users using various devices.
• Identity providers: They verify the identities of users or customers and provide security tokens.
• Client requests are handled via API Gateway.
• All of the system's material is contained in static content.
• Management - Determines failures and balances services across nodes.
• A tool for determining the path of communication among microservices is called service discovery.
• Network connection of proxy servers and associated data centers is called a content delivery network.
• Information stored on a network of IT devices can be accessed remotely with the help of a remote service.

27. What design principles work best for resource representations?

The following are crucial considerations while creating a resource's representation format for a RESTful web service. −

• Understanding and use of the resource's representation format should be possible for both the server and the client.
• Completeness A format ought to be able to accurately depict a resource. A resource could contain another resource, for instance. Format ought to be able to depict both straightforward and intricate resource structures.
• Linkability is a format that needs to be able to handle situations where one resource links to another.

28. What does RESTful Webservices' statelessness entail?

A RESTful web service should not maintain a client state on the server in accordance with REST design. Statelessness is the term for this limitation. The client must transmit its context to the server, which can then store it and use it to perform the client's subsequent requests. For instance, the session identifier given by the client can be used to identify a server-maintained session.

29. What distinguishes monolithic, SOA, and microservices architectures from one another?

• With a monolithic architecture, all the software parts of a program are put together and neatly wrapped in one large container.
• A group of services that communicate with one another is referred to as a service-oriented architecture. Simple data exchange or the coordination of an action between two or even more services are both possible forms of communication.
• Microservice  Architecture is a type of architectural design that organizes an application as a group of tiny, independent services based on a business domain.

30. Do you think GraphQL is the best choice for creating microservice architecture?

Because GraphQL hides your microservice architecture from the customers, it works perfectly with microservices. From the front end, you want all the data to come from a small API, while from the back end, you want to divide it into microservices. The best technique I'm aware of to do both is by using GraphQL. It enables you to divide the backend into microservices while still giving each application a single API and enabling joins across data from various services.

31. What function does a URI serve in RESTful web services?

Uniform Resource Identifier is what URI stands for. In a REST architecture, a URI identifies each resource. Locating a resource or resources on the server hosting the web service is the purpose of a URI.

32. What do Web API Media type formatters do?

The Web API's Media type formatter includes:

• The foundation class used to handle serializing and deserializing solid objects is called MediaTypeFormatter.
• BufferedMediaTypeFormatter is an utility class that enables asynchronous formatters on top of the infrastructure for asynchronous formatters.

Frequently Asked Rest API interview questions

33. Describe REST.

Representational State Transfer is referred to as REST.

34. REST API: What is it?

An API, or application programming interface, is a software-to-software interface that permits communication and data sharing between otherwise independent applications. All data is regarded as resources in a REST API, and each resource is identified by a distinct standard resource identifier (URI).

35.RESTful web services, what exactly do you mean?

RESTful web services, which adhere to the REST architecture, are another name for REST API.

36. Cache-control headers: What are they?

To manage catching and achieve caching, cache-control headers are employed. Public, private, and No-Store are the three cache-control headers that are most frequently used.

37. What characteristics distinguish RESTful web services?

The following distinguishing characteristics of REStful online services:

• Server-client decoupling
• communication assistance
• thin, uniform interface
• Stateless
• layered approach
• Cacheable
• On-demand code

38. What does messaging mean in the context of RESTful internet services?

When a REST client wishes to send a request to the server using a REST API web service, they can do so using an HTTP application form, and the server is no different. In REST, this type of communication is known as messaging.

39. Why "Addressing" is important in RESTful internet services.

Addressing is the term used to describe how RESTful web services locate different sorts of resources using a URL on the REST server. Resources typically address a single or a number of resources.

40. Why is it simple to scale REST services?

Due to their statelessness, which prevents them from storing data from the server even since they are requested, REST services are scalable.

41. Idempotent methods: what are they?

Duplicate calls on the client side are known to result in problems since idempotent techniques are known to provide the same result even after the identical request has been submitted many times.

42. How can testing be done on RESTful web services?

Tools like Swagger and Postman, which allow users to examine query parameters, headers, and response headers, as well as document endpoints and convert them to XML and JSON, can be used to test RESTful web services.

Key Upshots

You can now approach the interviews with confidence because you have a good understanding of how to respond to some of the typical REST API interview questions.