Top 64 Web API Interview Questions and Answers

10/Oct/2024 | 12 minutes to read

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Here is a List of essential Web API Interview Questions and Answers for Freshers and mid level of Experienced Professionals. All answers for these Web API questions are explained in a simple and easiest way. These basic, advanced and latest Web API questions will help you to clear your next Job interview.

Web API Interview Questions and Answers

These interview questions are targeted for ASP.NET Web API. You must know the answers of these ASP.NET Web API interview questions to clear a .NET developer interview.

1. What is the RESTful API?

Web service APIs that comply with REST principles are called RESTful APIs. You can define the RESTful APIs using:

• A base URI - Unique resource identifier.
• HTTP methods - GET, PUT, POST, PATCH, DELETE mapped with CRUD operations.
• A media type for data - used to exchange the information using data formats such as JSON (JavaScript Object Notation) and XML.

2. What are ASP.NET Web APIs?

ASP.NET Web APIs - A platform to build secure RESTful APIs which can be accessed by a broad range of clients including browsers, Daemon Apps, and mobiles devices. In ASP.NET, you can use the same framework to build web pages and services. For more visit ASP.NET Web APIs

3. How will you differentiate SOAP APIs from RESTful APIs?

REST APIs are lightweight as there is no built-in security and transaction compliance. Because of their lightweight REST APIs are good choices for mobile application development, IoT (Internet of Things) and serverless computing. SOAP APIs provide built-in security, error handling, and transaction compliance which makes them heavier as compared to REST APIs. And REST APIs are fast as no additional processing is required.
SOAP APIs work well in distributed environments whereas REST APIs are used for point-to-point communication. SOAP uses XML message format whereas REST APIs use JSON message format smaller than XML.
For more visit SOAP and REST API and SOAP vs REST.

4. What are the methods supported by ASP.NET Web API?

ASP.NET Web API offers four main HTTP methods which can be mapped to CRUD operations.

• GET is used to retrieve the resource at specified URI.
• PUT is used to update a resource at specified URI and can create a new resource if the server allows the client to specify a new URI.
• POST is used to create new resources.
• DELETE performs deletion of a resource at specified URI.
• PATCH also used to update a resource by specifying a set of instructions - means how the resource should be modified.

5. Describe ASP.NET Core Web API.

Web API is a framework that is used to develop REST APIs that can be consumed by any client. ASP.NET Core provides the ability to develop RESTful services also known as Web APIs. Web API uses the concept of controllers derived from the ControllerBase class to handle the requests.

6. Differentiate MVC and Web API.

ASP.NET MVC is a framework to develop web apps and APIs using MVC architecture. When you are driving your API controller class from Controller base class then it adds the support for views but when you want to create Web APIs then derive your API controller class from ControllerBase class. So MVC is just a design pattern and ASP.NET Web API is a framework to build RESTful APIs.

7. Explain commonly used attributes in ASP.NET Web API.

Commonly used attributes are Route, Bind, HttpGet, Consumes, Produces etc. For more you can visit Attributes.

8. What behaviors does the ApiController attribute provide?

9. How to disable automatic HTTP 400 responses in Web API?

You can disable the automatic trigger of HTTP 400 responses by setting SuppressModelStateInvalidFilter to 'True' in Startup.ConfigureServices as below.

    services.AddControllers()
    .ConfigureApiBehaviorOptions(options =>
    {
    options.SuppressModelStateInvalidFilter = true;
    });

10. Explain the controller action return types that ASP.NET Core web API provides.

Versioning in ASP.NET Core Web API:

11. How would you implement versioning in an ASP.NET Core Web API?

12. Explain the different versioning strategies (URI versioning, header versioning, query string versioning) and their pros and cons.

13. How can you handle breaking changes in a versioned API?

Authentication and Authorization:

14. Explain the difference between Authentication and Authorization in the context of ASP.NET Core Web API.

15. How would you implement JWT (JSON Web Token) authentication in an ASP.NET Core Web API?

16. What does JWT token contain? Explain about it.

For more about JWT Token visit JWT Introduction and JWT Token.

17. How to validate JWT token in .NET Web APIs?

For more visit Create And Validate JWT Token In .NET 5.0.

18. What is the role of Identity Server in an ASP.NET Core Web API application?

19. How would you implement role-based authorization in an ASP.NET Core Web API?

Performance and Caching:

20. How can you improve the performance of an ASP.NET Core Web API?

21. Explain the different caching techniques (in-memory caching, distributed caching, response caching) available in ASP.NET Core.

22. How would you implement response caching in an ASP.NET Core Web API?

23. What is the purpose of the IMemoryCache interface in ASP.NET Core?

Advanced Routing:

24. How would you implement attribute routing in an ASP.NET Core Web API?

25. Explain the concept of constraint routing and provide an example.

26. How can you implement custom route constraints in an ASP.NET Core Web API?

Dependency Injection:

27. Explain the concept of Dependency Injection and its benefits.

28. How would you register and resolve dependencies in an ASP.NET Core Web API?

29. In dependency injection, how do constructor injection, property injection, and method injection differ in terms of their implementation and usage?

30. How can you resolve circular dependencies in an ASP.NET Core Web API?

Logging and Monitoring:

31. Explain the built-in logging providers in ASP.NET Core and their use cases.

32. How would you implement custom logging in an ASP.NET Core Web API?

33. What is the role of Application Insights in monitoring an ASP.NET Core Web API?

34. How can you set up distributed tracing in an ASP.NET Core Web API?

Advanced Topics:

35. Explain the concept of gRPC (gRPC Remote Procedure Calls) and its advantages over traditional REST APIs.

36. How would you implement GraphQL in an ASP.NET Core Web API?

37. What are the benefits of using SignalR in an ASP.NET Core Web API for real-time communication?

38. How can you implement event-driven architectures using Message Queues (e.g., RabbitMQ, Azure Service Bus) in an ASP.NET Core Web API?

Error Handling:

39. How would you implement a global exception handler in an ASP.NET Core Web API?

40. What are the different types of HTTP status codes you can use to indicate different error scenarios in a Web API?

41. How would you handle and log unhandled exceptions in an ASP.NET Core Web API?

42. Explain the concept of model validation in Web APIs and how you would handle validation errors.

Request/Response Formatting:

43. How would you implement content negotiation in an ASP.NET Core Web API to support different response formats (JSON, XML, etc.)?

44. What are the different ways to format the request and response bodies in a Web API?

45. How would you handle large file uploads and downloads in a Web API?

46. Explain the concept of data shaping (projections) and how you would implement it in an ASP.NET Core Web API.

47. How will you format response data in ASP.NET Core Web API?

For more visit https://learn.microsoft.com/en-us/aspnet/core/web-api/advanced/formatting?view=aspnetcore-8.0

48. Explain the custom formatters.

Security:

49. How would you implement rate limiting in an ASP.NET Core Web API to prevent abuse or denial of service attacks?

50. Explain the concept of Cross-Site Request Forgery (CSRF) and how you would mitigate it in a Web API.

51. How would you implement input validation to prevent security vulnerabilities like SQL injection and cross-site scripting (XSS)?

52. Explain the concept of API keys and how you would implement them in an ASP.NET Core Web API for authentication and authorization.

Testing:

53. What are the different types of testing you would perform for an ASP.NET Core Web API?

54. How would you implement unit testing for an ASP.NET Core Web API controller?

55. Explain the concept of integration testing and how you would implement it for a Web API.

56. How would you perform load testing and stress testing for an ASP.NET Core Web API?

Deployment and Monitoring:

Explain the different deployment strategies (blue-green, canary, rolling) and when to use them for an ASP.NET Core Web API.

57. How would you implement health checks and monitoring for an ASP.NET Core Web API?

58. What are the benefits of containerizing an ASP.NET Core Web API, and how would you deploy it to a container orchestration platform like Kubernetes?

59. Explain the concept of observability (logging, metrics, tracing) and how you would implement it in an ASP.NET Core Web API.

Others:

60. How to handle JSON Patch requests in an ASP.NET Core web API?

61. How will you choose from a class library project or Web API?

62. What is OpenApi?

63. What is Swagger?

64. How will you generate web API documentation using Swagger/OpenAPI?

Some General Interview Questions for Web API

1. How much will you rate yourself in Web API?

When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like Web API, So It's depend on your knowledge and work experience in Web API. The interviewer expects a realistic self-evaluation aligned with your qualifications.

2. What challenges did you face while working on Web API?

The challenges faced while working on Web API projects are highly dependent on one's specific work experience and the technology involved. You should explain any relevant challenges you encountered related to Web API during your previous projects.

3. What was your role in the last Project related to Web API?

This question is commonly asked in interviews to understand your specific responsibilities and the functionalities you implemented using Web API in your previous projects. Your answer should highlight your role, the tasks you were assigned, and the Web API features or techniques you utilized to accomplish those tasks.

4. How much experience do you have in Web API?

Here you can tell about your overall work experience on Web API.

5. Have you done any Web API Certification or Training?

Whether a candidate has completed any Web API certification or training is optional. While certifications and training are not essential requirements, they can be advantageous to have.

Conclusion

We have covered some frequently asked Web API Interview Questions and Answers to help you for your Interview. All these Essential Web API Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any Web API Interview if you face any difficulty to answer any question please write to us at info@qfles.com. Our IT Expert team will find the best answer and will update on the portal. In case we find any new Web API questions, we will update the same here.