HTTP, APIs and WebSocket Interview Questions

All 123 questions

1. What happens from entering a URL in a browser to receiving and rendering the page?

   Asked in 6 of 337 interviews · last asked Aug 25 · Concept · Mid-level

   Show answer

   The browser checks caches and uses DNS if it needs the server's IP address. It reuses or opens a connection: usually TCP, with TLS for HTTPS; HTTP/3 uses QUIC. It sends an HTTP request and receives a response. For HTML, it parses the document, fetches resources, runs scripts, and calculates and draws the page layout.

   • Cached content, cached DNS results, and existing connections can skip some network steps.
   • HTTPS encrypts traffic and verifies the server's certificate; HTTP/3 uses QUIC over UDP with TLS.
   • The server processes the request and returns a status, headers, and usually a body; redirects require another request.
   • HTML builds the DOM; CSS determines styles. Layout calculates positions, and painting draws content.

   What the interviewer checks: The interviewer checks whether you can connect DNS, transport security, HTTP, and browser rendering in the right order.

   Other ways it was asked

   • “What happens on the networking side when you type a URL into a browser?”
   • “What happens behind the scenes from a networking and web browsing perspective when you type a URL into a browser?”
   • “What happens after you enter google.com in a browser and submit the request? Which services are involved, and where does the information go?”

2. What do common HTTP status codes mean?

   Asked in 5 of 337 interviews · last asked Oct 5 · Concept · Junior

   Show answer

   HTTP status codes are three-digit numbers that describe an HTTP response. The groups are 1xx for information, 2xx for success, 3xx for redirection, 4xx for client errors, and 5xx for server errors.

   • 200: OK; 201: resource created; 204: success with no response body.
   • 301: permanent redirect; 302: temporary redirect; 304: not modified, so reuse the cached response.
   • 400: bad request; 401: missing or invalid credentials; 403: forbidden; 404: not found; 429: too many requests.
   • 500: internal server error; 502: gateway received an invalid upstream response; 503: service temporarily unavailable.

   What the interviewer checks: The interviewer checks whether you understand response outcomes and can distinguish authentication, permission, client, and server problems.

   Other ways it was asked

   • “What are HTTP status codes?”
   • “What are the different HTTP response status codes?”
   • “What are the common HTTP status codes?”

3. What is CORS, and how does it affect cross-origin requests?

   Asked in 3 of 337 interviews · last asked Sep 16 · Concept · Mid-level

   Other ways it was asked

   • “What is CORS?”
   • “What is CORS, and how does it work?”

4. What are WebSockets, and when would you use them?

   Asked in 2 of 337 interviews · last asked Mar 5 · Concept · Mid-level

   Other ways it was asked

   • “What are WebSockets?”

5. How do HTTP/1, HTTP/2, and HTTP/3 differ at the protocol level?

   Asked in 2 of 337 interviews · last asked Oct 8 · Concept · Mid-level

   Other ways it was asked

   • “What is the difference between HTTP/1 and HTTP/2?”

6. What are the components of an HTTP request?

   Asked in 2 of 337 interviews · last asked Oct 8 · Concept · Junior

   Other ways it was asked

   • “What are the components of an HTTP response?”
   • “What components are included in an HTTP POST request?”

7. How does a point-of-sale transaction flow from the register to the server?

   Asked once · last asked Jun 8 · Design · Mid-level

   Other ways it was asked

   • “How does the database fit into the flow of a point-of-sale transaction from the register to the server?”

8. How does Kafka replicate messages to another node, and what protocol does it use?

   Asked once · last asked Jul 22 · Concept · Senior

9. How would you extract frames from an RTSP stream for face recognition?

   Asked once · last asked Sep 22 · Tooling · Mid-level

10. What are SFTP, FTP, HTTP, HTTPS, and SMTP used for, and how do they differ?

    Asked once · last asked Feb 14 · Concept · Mid-level

11. How would you use socket integration to support real-time messaging in a chat application?

    Asked once · last asked Feb 18 · Concept · Mid-level

12. If multiple websites are hosted on one server, resolve to the same IP address, and use the same port (for example, HTTPS on port 443), how does the server know which website to serve?

    Asked once · last asked Mar 2 · Concept · Mid-level

13. If you were designing the client-server protocol yourself, for example as a browser developer, how would you make sure the server returns the website corresponding to the domain the user enters?

    Asked once · last asked Mar 2 · Concept · Mid-level

14. What happens internally when a user clicks a URL in a browser?

    Asked once · last asked Mar 10 · Concept · Junior

15. What happens on the server side, and how does the server handle a request?

    Asked once · last asked Mar 10 · Concept · Junior

16. How would you handle a third-party API's 429 Too Many Requests responses in PHP, including immediate backoff, respecting Retry-After, and system-wide throttling or queuing to prevent repeated rate-limit errors?

    Asked once · last asked Mar 26 · Scenario · Senior

    Other ways it was asked

    • “When a third-party API rate-limits you, how do you handle 429 Too Many Requests in PHP? What do you do immediately for that request, such as backing off and respecting Retry-After, and what system-wide throttling or queuing do you implement to prevent repeated 429 responses?”

17. How do sockets enable real-time communication between a client and a server, and when would you use them?

    Asked once · last asked Apr 9 · Concept · Mid-level

18. After the PC receives an IP address, what process does it follow when you enter a website's domain name?

    Asked once · last asked Apr 13 · Concept · Junior

19. What are short polling and long polling, and how do they differ?

    Asked once · last asked Apr 17 · Concept · Mid-level

20. When you enter example.com in a web browser and press Enter, what happens next on your PC?

    Asked once · last asked Apr 24 · Concept · Junior

    Other ways it was asked

    • “When you enter google.com in a web browser and press Enter, what happens next on your PC?”

21. Are GraphQL requests always sent using POST, or can a query use another HTTP method?

    Asked once · last asked Apr 27 · Concept · Mid-level

22. How do you handle data communication between an Android app and a backend, including encoding or encrypting data and sending and receiving tokens?

    Asked once · last asked May 7 · Scenario · Mid-level

23. What does the `-L` option do in cURL?

    Asked once · last asked May 13 · Concept · Junior

24. What does the `-H` option do in cURL?

    Asked once · last asked May 13 · Concept · Junior

25. How do GET and POST requests differ from WordPress's WP_Query?

    Asked once · last asked Jun 4 · Concept · Mid-level

    Other ways it was asked

    • “What is the difference between GET and POST requests, and how does WP_Query work?”

26. When a user enters a URL in a browser and presses Enter, can you explain the complete end-to-end journey of the request and response, from the user's device until the webpage is displayed, including the technologies and terminology involved?

    Asked once · last asked Jun 11 · Concept · Junior

27. Suppose you have a Node.js, Django, or FastAPI server. How is a request routed through the system?

    Asked once · last asked Jun 11 · Concept · Mid-level

28. Can you explain the full traffic flow when you access google.com from your laptop, until the page content appears?

    Asked once · last asked Jun 11 · Concept · Mid-level

29. Briefly explain, in order, what happens from entering a URL in a browser until the page is rendered, including DNS resolution, connection establishment, starting encrypted communication, sending the request and receiving the response, and browser rendering.

    Asked once · last asked Jun 22 · Concept · Junior

30. In your experience, what are some key considerations when designing a back end system to support real-time communication features?

    Asked once · last asked Jul 16 · Design · Senior

31. What is CORS, and how does it relate to API security?

    Asked once · last asked Jul 16 · Concept · Mid-level

32. How can we implement domain-based routing in our application?

    Asked once · last asked Jul 16 · Tooling · Senior

33. What response code would you expect if the HTTP method in the request were not supported by the resource?

    Asked once · last asked Jul 16 · Concept · Junior

34. How does WebSocket differ from a standard request-response interaction?

    Asked once · last asked Jul 16 · Concept · Junior

35. Which HTTP response headers and request details would you compare with Chrome to determine whether a Safari download failure involves CORS, Content-Disposition, MIME type, or cookies and sessions?

    Asked once · last asked Jul 16 · Scenario · Senior

36. What happens when you type google.com into your browser?

    Asked once · last asked Jul 15 · Concept · Mid-level

37. How do you integrate APIs into a mobile application?

    Asked once · last asked Jul 22 · Concept · Junior

38. What are the HTTP status code classes, and what does each class indicate?

    Asked once · last asked Jul 22 · Concept · Junior

39. How would you design a mail transfer agent capable of handling nearly one billion emails per hour?

    Asked once · last asked Jul 25 · Design · Senior

40. How would you make an HTTP request in Python, pass parameters, and retrieve the response?

    Asked once · last asked Jul 26 · Write code · Junior

41. What is the difference between the Reply-To and Return-Path fields in an email header?

    Asked once · last asked Jul 27 · Concept · Mid-level

42. What web servers and services are needed to serve a website's content after deployment?

    Asked once · last asked Jul 27 · Concept · Junior

43. When inspecting a new website's network requests for scraping, what do you look for?

    Asked once · last asked Jul 28 · Tooling · Mid-level

44. Would a WebSocket-based approach scale to hundreds of millions of users?

    Asked once · last asked Jul 28 · Design · Senior

45. What are the differences between Nginx and Apache, and when would you use each?

    Asked once · last asked Jul 30 · Concept · Mid-level

46. How do you choose communication protocols for IoT integrations?

    Asked once · last asked Aug 6 · Concept · Mid-level

    Other ways it was asked

    • “What are common communication protocols used in IoT, and when would you use them?”

47. What are Server-Sent Events, and when would you use them?

    Asked once · last asked Aug 13 · Concept · Mid-level

48. What is the difference between Server-Sent Events and WebSockets?

    Asked once · last asked Aug 13 · Concept · Mid-level

49. Build a simple list view using data from a public API.

    Asked once · last asked Aug 19 · Write code · Mid-level

50. Create an Xcode project that fetches data from a URL and displays the results in a list.

    Asked once · last asked Aug 19 · Write code · Mid-level

51. Build a simple list view that fetches users from the GitHub API and displays each user's login as the title and any available field as the subtitle, without pagination.

    Asked once · last asked Aug 19 · Write code · Mid-level

52. How would you design a proxy between an application and a database to forward requests and responses?

    Asked once · last asked Aug 21 · Design · Senior

53. Which transport mechanism would you use for communication between an MCP client and server?

    Asked once · last asked Aug 26 · Concept · Mid-level

54. How do you handle WebSocket connections for an online game, especially with concurrent users and reconnects?

    Asked once · last asked Aug 26 · Design · Senior

    Other ways it was asked

    • “How would you use WebSockets to reconnect clients, rehydrate game state, and manage channel subscriptions in an online game?”

55. How would you handle multiple game sessions and separate socket channels?

    Asked once · last asked Aug 26 · Design · Mid-level

56. When I click a button in a React component and expect a list of products from an API, what are the steps from click to the list showing on the screen?

    Asked once · last asked Sep 2 · Scenario · Mid-level

57. What happens when you type example.com into a browser?

    Asked once · last asked Sep 9 · Concept · Mid-level

    Other ways it was asked

    • “What happens when you type apple.com into a browser?”

58. How would you chunk a large file for upload, and how would you choose the chunk size?

    Asked once · last asked Sep 9 · Scenario · Mid-level

59. How would you notify the front end when an asynchronous chatbot job is complete?

    Asked once · last asked Sep 10 · Design · Mid-level

60. What problem does IHttpClientFactory solve compared to creating a new HttpClient manually, and how do you handle DNS changes and resiliency?

    Asked once · last asked Sep 10 · Concept · Senior

61. How do you process an RTSP video stream?

    Asked once · last asked Sep 11 · Tooling · Mid-level

62. How would you design real-time voice input for a chat, with an experience similar to a phone call?

    Asked once · last asked Sep 18 · Design · Senior

63. How would you handle interruptions and connection loss in a real-time voice chat to maintain a good user experience?

    Asked once · last asked Sep 18 · Scenario · Senior

64. Where would you initialize a WebSocket in a React component, how would you handle reconnection, and where would you clean up the connection?

    Asked once · last asked Sep 18 · Tooling · Mid-level

65. What is a reverse proxy and why is it important in web applications?

    Asked once · last asked Sep 21 · Concept · Mid-level

66. Which one is more secure, GET or POST, or are both secure?

    Asked once · last asked Sep 21 · Concept · Mid-level

67. How would you connect a computer vision application to an RTSP stream from a camera?

    Asked once · last asked Sep 22 · Tooling · Mid-level

68. What would you check if a webhook in production is failing?

    Asked once · last asked Sep 25 · Scenario · Mid-level

69. How would you manage subsecond response latency in voice agents, including WebSocket communication and fallback handling?

    Asked once · last asked Sep 30 · Scenario · Senior

70. How would you update a dashboard in real time when webhooks are received?

    Asked once · last asked Oct 1 · Design · Mid-level

71. When making an HTTP request to a very fast service in another container, would you use synchronous or asynchronous code, and why?

    Asked once · last asked Oct 6 · Scenario · Senior

72. How does client-side HTTP caching work, and are all requests cached?

    Asked once · last asked Oct 6 · Concept · Mid-level

73. How does HTTP caching work with `Cache-Control` and `ETag`?

    Asked once · last asked Oct 7 · Concept · Mid-level

74. What happens from the moment you enter a URL in a browser until the browser receives the HTML?

    Asked once · last asked Oct 7 · Concept · Mid-level

75. Explain how hashing, CDNs, and the browser rendering pipeline affect page loading.

    Asked once · last asked Oct 7 · Concept · Mid-level

    Other ways it was asked

    • “Explain how caching, CDNs, and the browser rendering pipeline affect page loading.”

76. What problem does HTTP/3 solve by using QUIC?

    Asked once · last asked Oct 7 · Concept · Mid-level

77. What should a web application do when a WebSocket connection disconnects?

    Asked once · last asked Oct 8 · Scenario · Mid-level

78. What happens when someone opens a website, and how does the request flow from the browser to the server?

    Asked once · last asked Oct 8 · Design · Mid-level

79. What happens after a user enters a domain name in the browser's address bar?

    Asked once · last asked Oct 12 · Concept · Junior

80. How does a browser determine which protocol to use, and does the protocol affect the subsequent request sequence?

    Asked once · last asked Oct 12 · Concept · Junior

81. When you type google.com in Firefox and press Enter, what happens in the background?

    Asked once · last asked Oct 13 · Concept · Mid-level

82. Explain the complete request lifecycle from a frontend click to the Django database response.

    Asked once · last asked Oct 14 · Concept · Mid-level

83. When an external service becomes slow, how can that cause a user-facing error, and what might the user see?

    Asked once · last asked Oct 14 · Scenario · Mid-level

84. What HTTP status code or response information does a client receive when a load balancer terminates a request due to a timeout?

    Asked once · last asked Oct 14 · Concept · Mid-level

85. How would you configure a POP email account in Microsoft Outlook?

    Asked once · last asked Oct 19 · Tooling · Junior

86. If a user clicks through from an external news site with browser privacy features enabled, can you still identify the referral source?

    Asked once · last asked Oct 19 · Scenario · Mid-level

87. Build a simple chat service where a message entered in one browser appears in the other browser.

    Asked once · last asked Jan 20 · Write code · Mid-level

88. What does a 401 error mean when you make a request using Postman?

    Asked once · last asked Jul 31 · Concept · Junior

    Other ways it was asked

    • “What does a 403 error mean when you make a request using Postman?”

89. What protocol is used to access a Windows file share?

    Asked once · last asked Jan 29 · Concept · Junior

90. What happens at the HTTP level when a request reaches a web server?

    Asked once · last asked Mar 2 · Concept · Junior

91. What does HTTP status code 300 indicate?

    Asked once · last asked Apr 10 · Concept · Junior

92. What is HTTP status code 500 used for?

    Asked once · last asked Apr 10 · Concept · Junior

93. What are timeouts, and how should an application handle them?

    Asked once · last asked Apr 13 · Concept · Mid-level

94. What can happen when a web application does not configure CORS?

    Asked once · last asked Apr 15 · Concept · Junior

95. How do you send a GraphQL request to a specific endpoint?

    Asked once · last asked Apr 27 · Concept · Junior

96. What cURL command would you use to download a file?

    Asked once · last asked May 13 · Tooling · Junior

97. Can you name three HTTP headers?

    Asked once · last asked May 19 · Concept · Junior

98. What components make up an HTTP request and response, apart from the response status code?

    Asked once · last asked May 28 · Concept · Junior

    Other ways it was asked

    • “What components, other than the status code, are included in an HTTP request or response?”

99. What is Modbus?

    Asked once · last asked Jun 26 · Concept · Junior

100. What protocols are commonly used for APIs?

     Asked once · last asked Jul 16 · Concept · Junior

101. Is HTTP stateless or stateful?

     Asked once · last asked Jul 24 · Concept · Junior

102. What does an HTTP 301 response mean when a user visits a website?

     Asked once · last asked Jul 30 · Concept · Junior

103. How can you determine where an HTTP redirect sends a user?

     Asked once · last asked Jul 30 · Tooling · Junior

104. Where can HTTP redirects be configured on a web server?

     Asked once · last asked Jul 30 · Concept · Junior

105. What is a protocol? Give an example, particularly OAI-PMH.

     Asked once · last asked Aug 3 · Concept · Junior

106. How would you handle a video stream in an application?

     Asked once · last asked Aug 6 · Scenario · Mid-level

107. What is web browsing, and how does it work?

     Asked once · last asked Aug 14 · Concept · Junior

108. What is the use of the iSCSI protocol in storage?

     Asked once · last asked Aug 18 · Concept · Junior

109. What happens after a browser completes a DNS lookup?

     Asked once · last asked Aug 25 · Concept · Mid-level

110. What is polling, and when would you use it?

     Asked once · last asked Sep 4 · Concept · Junior

111. How does the Python requests library work?

     Asked once · last asked Sep 17 · Concept · Junior

112. Where should frontend-to-gateway traffic routing be handled?

     Asked once · last asked Sep 21 · Design · Mid-level

113. What does %20 translate to in the URL?

     Asked once · last asked Sep 23 · Concept · Junior

114. What does %40 represent in a URL?

     Asked once · last asked Sep 23 · Concept · Junior

115. Can you explain how email works? For example, if I send an email from my computer to a friend in Australia, what is happening?

     Asked once · last asked Sep 24 · Concept · Junior

116. How can you call a REST API from a front end?

     Asked once · last asked Sep 30 · Concept · Junior

117. What is an API request?

     Asked once · last asked Oct 3 · Concept · Junior

118. What is the difference between HTTP 400 and 500 status codes?

     Asked once · last asked Oct 8 · Concept · Junior

119. What do HTTP 401 and 403 mean, and when should each be used?

     Asked once · last asked Oct 8 · Concept · Junior

     Other ways it was asked

     • “What does an HTTP 403 status code mean?”
     • “What does an HTTP 401 status code mean?”

120. What is the purpose of the HTTP Accept header?

     Asked once · last asked Oct 11 · Concept · Junior

121. How can browser caching be controlled, including clearing the cache or setting cache parameters?

     Asked once · last asked Oct 12 · Tooling · Junior

122. What does 200 OK mean in an HTTP response?

     Asked once · last asked Oct 13 · Concept · Junior

123. If you were designing a simple web app, can you describe the basic request flow from browser to database and back, naming the main components involved?

     Asked once · last asked Oct 20 · Design · Junior

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How this list is made

Every question here was asked by a real interviewer in a real job interview that a candidate ran MeetAssist in. After the call, the interviewer's questions are pulled from the transcript. Practice sessions, tests, exams and anything that was not a job interview are dropped.

Questions are rewritten so they make sense on their own: names of people, employers and clients are removed, and speech-to-text mistakes are fixed. Small talk, logistics and questions about one candidate's own résumé are left out. Rephrasings of the same question are merged, and the count is the number of different interviews it came up in.

The interviews come from candidates who use MeetAssist, so they lean towards software, data and AI roles: the shares describe these interviews, not every Computer Networks interview. Answers to the most asked questions are written and checked by an editor; a "common mistake" is shown only when reviews of real answers in these interviews show it, with the count.

337 interviews, 208 candidates, Nov 2025 to Oct 2026. Updated every month with new interviews.