I applied through college or university. The process took 1 day.

I was given a real-world systems programming task in the interview to implement a real-time log-watching solution, similar to tail -f in UNIX. The log file was on the same machine as the server code and was in append-only mode. The objective was to build a C++ server that streams new log lines to multiple clients in real time using WebSockets. The test had three core parts:

• A server that efficiently reads a large log file and streams only new lines.
• A browser-based client (at http://localhost/log) that renders the last 10 lines on first load and updates live without refreshing.
• The solution had to be highly optimized, considering that the log file could be several GBs, so scanning the whole file was discouraged. We weren’t allowed to use external libraries like Boost or tailing utilities — which made implementing line-seeking and efficient file I/O trickier.

I used seekg and reverse traversal to get the last 10 lines and then continuously polled the file for changes using non-blocking reads. Overall, it was a great systems design + low-level coding challenge testing real-time communication, efficient file handling, and web integration. I qualified the first round. Then 2nd round was director's round, which was mainly resume based + some networking and web development questions and 1-2 DSA questions. I didn't make through it.

How would you retrieve the last 10 lines of a log file that is several GB in size, without reading the entire file into memory?