35+ Web API Interview Questions and Answers (2024)

Are you preparing for a Web API interview and looking for some expert guidance on the types of questions you may encounter? 

Look no further! 

In today’s fast-paced technological landscape, the demand for Web API developers is skyrocketing. As more businesses embrace digital transformation, they require reliable Web API solutions to communicate with their applications and systems. However, with the growing demand for this skillset, competition for job openings has become fierce. 

So, without further ado, let’s dive into the exciting world of Web APIs!

Top 35+ Web API Interview Questions and Answers to Ace Your 2024 Job Interview

To help you stand out, we’ve compiled a list of the top 35+ Web API interview questions and answers for 2024, ensuring that you have the knowledge and confidence to excel in your upcoming interview. 

1. What is a Web API?

A Web API, or Web Application Programming Interface, is a set of programming protocols and standards for accessing a web-based software application or web tool. It defines the way in which different software systems communicate with each other using the internet.

2. What are the different types of Web APIs?

There are three types of Web APIs:

  • Open APIs (also known as external or public APIs) are available to developers and other users with minimal restrictions.
  • Internal APIs (or private APIs) are designed to be used within a company or organization and are not publicly available.
  • Partner APIs are designed to be shared with select partners or third-party developers.
3. What are the benefits of using a Web API?

The benefits of using a Web API include:

  • Interoperability between different software systems
  • Reusability of code
  • Faster development time
  • Reduced development costs
  • Increased efficiency
  • Improved scalability
4. What is RESTful API?

RESTful API is an architectural style for building web services using HTTP protocols. REST, which stands for Representational State Transfer, is a lightweight alternative to the more complex SOAP (Simple Object Access Protocol) web services.

5. What is SOAP?

SOAP is a protocol for exchanging structured information in the implementation of web services in computer networks. SOAP can use different transport protocols such as HTTP, SMTP, and TCP.

6. What is the difference between REST and SOAP?

The key differences between REST and SOAP include:

  • REST uses simpler protocols such as HTTP and JSON, while SOAP uses XML and more complex messaging protocols.
  • REST is more lightweight and faster than SOAP.
  • REST is more flexible and can work with any data format, while SOAP is more rigid and requires strict XML formatting.
7. What is JSON?

JSON, or JavaScript Object Notation, is a lightweight data-interchange format that is easy for humans to read and write and easy for machines to parse and generate. JSON is a text format that is completely language-independent.

8. What is XML?

XML, or Extensible Markup Language, is a markup language that is used to encode documents in a format that is both human-readable and machine-readable. XML is designed to be self-descriptive and can be used to define custom tags and document structures.

9. What is HTTP?

HTTP, or Hypertext Transfer Protocol, is a protocol that is used for communication between web servers and clients. HTTP defines the way in which web browsers and servers exchange information, including how requests are made and how responses are returned.

10. What is HTTPS?

HTTPS, or Hypertext Transfer Protocol Secure, is a secure version of HTTP that encrypts all data transmitted between a web server and a client. HTTPS is designed to prevent eavesdropping, tampering, and message forgery.

11. What is an HTTP verb?

HTTP verbs are used to define the action that needs to be performed on a resource. The most commonly used HTTP verbs are GET, POST, PUT, and DELETE. GET is used to retrieve data, POST is used to create a new resource, PUT is used to update an existing resource, and DELETE is used to delete a resource.

12. What is a RESTful API?

A RESTful API is a type of web API that uses HTTP requests to access and manipulate resources. It is based on the REST architectural style, which stands for Representational State Transfer. RESTful APIs are characterized by their use of HTTP verbs and their adherence to certain principles such as statelessness, cacheability, and layered architecture.

13. What is a resource in Web API?

In Web API, a resource is any piece of data that can be accessed and manipulated using HTTP requests. Resources can include anything from a single value, such as a string or number, to a more complex object, such as a customer or order. Each resource is identified by a unique URL or URI.

14. What is a request header in Web API?

A request header is an HTTP header that provides additional information about the client making the request or the content being requested. Request headers can include information such as the Accept-Encoding, Accept-Language, and User-Agent headers, which provide information about the client’s capabilities and preferences.

15. What is a response header in Web API?

A response header is an HTTP header that provides additional information about the response being sent by the server. Response headers can include information such as the Content-Type, Content-Length, and Cache-Control headers, which provide information about the type and size of the response, as well as caching instructions.

16. What is CORS?

CORS stands for Cross-Origin Resource Sharing, which is a mechanism that allows resources on a web page to be requested from a different domain than the one that served the original page. CORS is used to enable web applications to securely access resources from different origins, while preventing cross-site scripting attacks.

17. What is a middleware in Web API?

Middleware is software that sits between an application’s client and server, providing additional functionality such as authentication, logging, and error handling. In Web API, middleware is often used to handle cross-cutting concerns such as security and caching.

18. What is a query string in Web API?

A query string is a part of a URL that contains additional data that can be used by the server to perform a specific action. Query strings are commonly used in Web API to pass parameters to a resource, such as filtering or sorting options. They are typically appended to the end of a URL, separated by a question mark.

19. What is the purpose of HTTP verbs in Web API?

HTTP verbs are used to define the type of operation that the client wants to perform on the server. The most commonly used HTTP verbs are GET, POST, PUT, and DELETE.

20. What is the difference between HTTP GET and POST methods?

GET and POST are two commonly used HTTP methods. The key difference between these two methods is that GET requests are used to retrieve data from a server, while POST requests are used to send data to a server for processing.

21. What is the difference between SOAP and RESTful Web Services?

SOAP and RESTful Web Services are two popular architectures for building web services. SOAP (Simple Object Access Protocol) is a protocol that uses XML messages to exchange information between web services, while REST (Representational State Transfer) is an architectural style that uses HTTP to transfer data between client and server.

22. What is a RESTful API?

A RESTful API is an architectural style for building web services that uses HTTP verbs (GET, POST, PUT, DELETE) to interact with resources, which are identified by URLs.

23. What is the purpose of URI in Web API?

URI (Uniform Resource Identifier) is used to uniquely identify a resource in the Web API. It is composed of a scheme, host, and path.

24. What is Web API routing?

Web API routing is a mechanism that maps incoming requests to the appropriate controller and action method. It defines a URL pattern that the Web API uses to match the incoming request and invoke the appropriate action method.

25. What is the difference between synchronous and asynchronous Web API calls?

Synchronous Web API calls block the execution of the program until the response is received, whereas asynchronous Web API calls do not block the execution of the program and allow it to continue running until the response is received.

26. What is Web API versioning?

Web API versioning is a technique used to manage changes to the API over time. It allows developers to create different versions of the API that can be used by different clients, without breaking the existing functionality of the API.

27. What is Swagger in Web API?

Swagger is an open-source tool that is used to document Web APIs. It allows developers to generate interactive API documentation that describes the API’s resources, operations, and parameters.

28. What is the difference between PUT and POST methods in HTTP?

PUT and POST are HTTP methods used to send data to a server. The key difference between PUT and POST methods is that PUT is idempotent, meaning that it can be called multiple times with the same set of parameters and the result will be the same.

On the other hand, POST is not idempotent and can be called multiple times with the same parameters resulting in different outcomes.

29. What is the purpose of the OPTIONS method in HTTP?

The OPTIONS method is used to determine which HTTP methods are supported by a server for a specific URL. When a client sends an OPTIONS request to a server, the server responds with a list of HTTP methods that are allowed for the requested resource. This can be useful for clients that need to dynamically determine what actions are available for a given resource.

30. What is a Webhook?

A webhook is a method of augmenting or altering the behavior of a web application by providing a callback URL that the application will call when certain events occur. Webhooks are typically used to trigger an action in response to an event, such as updating a database or sending a notification to a user.

31. What is OAuth?

OAuth (Open Authorization) is an open standard for authorization that allows users to grant third-party applications access to their resources without sharing their credentials.

OAuth is commonly used by web applications to authenticate users and access resources on their behalf, such as posting to social media or accessing cloud storage.

32. What is the difference between Authentication and Authorization?

Authentication is the process of verifying the identity of a user, device, or system. This is typically done using a username and password, or other means of identification such as a fingerprint or smart card.

Authorization, on the other hand, is the process of determining what actions a user is allowed to perform on a system, based on their authenticated identity.

33. What is a RESTful API?

A RESTful API is an API that conforms to the principles of REST architecture. This means that the API uses HTTP methods to access and manipulate resources, and typically returns data in a format such as JSON or XML.

RESTful APIs are often used in modern web applications due to their simplicity and scalability.

34. What is a Web API request and response?

A Web API request is a message sent by the client application to the server to perform a particular action, such as retrieving data or updating information. The Web API response is the message sent back from the server to the client application containing the requested data or status of the action.

35. What is versioning in Web APIs?

Versioning in Web APIs is the process of maintaining multiple versions of the same API. This is important when new features or changes are made to an existing API that may break existing client applications. Versioning allows developers to maintain backward compatibility with existing applications while introducing new features.

36. What are the different types of versioning in Web APIs?

The different types of versioning in Web APIs are URL versioning, request parameter versioning, header versioning, and media type versioning.

  • URL versioning involves including the version number in the URL of the API.
  • Request parameter versioning involves including the version number as a parameter in the request.
  • Header versioning involves including the version number in the header of the request or response.
  • Media type versioning involves using different media types for different versions of the API.
37. What is HATEOAS?

HATEOAS stands for Hypermedia as the Engine of Application State. It is a principle of RESTful APIs that allows clients to interact with resources through hyperlinks embedded in the response.

With HATEOAS, the client does not need to know the specific URLs of the resources, as they are provided dynamically by the server in the response.

38. What are some best practices for designing Web APIs?

Some best practices for designing Web APIs include using RESTful principles, providing clear and concise documentation, maintaining backward compatibility through versioning, using appropriate status codes for responses, implementing proper security mechanisms, and optimizing performance and scalability. Additionally, following industry standards and conventions can help make the API more intuitive and easier.

Web API is a crucial aspect of modern web development and plays a significant role in building responsive, interactive, and user-friendly applications. By preparing yourself with the answers to these top Web API interview questions, you can boost your chances of landing your dream job in the industry.

Remember to practice these questions with someone knowledgeable in the field, and don’t forget to showcase your enthusiasm and passion for web development during your interview. With these tips and insights, you are well on your way to acing your Web API interview and securing your place in this exciting and ever-evolving field. Good luck!

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