Passed the OA. I forgot the details about the OA, but it was easy. It was easier than any OA I've ever been through. (However, other teams from Fortinet have much more difficult OAs).

Then came the first round online HackerRank interview. It was 3 hours long and I was interviewed by the team members. There were 3 coding questions and some verbal technical questions. I didn't do well in the coding questions, but they still shortlisted me. C was the only allowed language in the coding part.

Coding: Leetcode 1290, 1779, 239.

For 1779 and 239, they would push you to code in the "dumb" way first if you can't think of an optimized way. But they won't give you time to code the optimized way, even if you got the idea.

Short answers:

1. Difference between a thread and a process.
2. Suppose you have a static variable declared outside any functions in a C program. Will the address be the same if it's declared in some function?
3. Will the address of a static variable always be the same between different runs of this program (no recompilation in between)?
4. What's the difference between a real-time OS and a general-purpose OS?