Initially telephonic round of interview of around an hour - questions based on trees and linked lists and computing the big O complexity of your solution, string manipulation, multi threading and thread synchronization(mutex locking), some questions on c++ related to shared libraries - such as a class is defined in a header file and included in 2 binaries, relink one binary but not the other - what is the runtime behavior, etc. It was a healthy discussion.
2nd round consists of an online test of 5 questions (I guess of 80 mins) - questions again based on LL, Trees, AVL tree balancing, string manipulation, playing around with bytes of memory, etc. I solved three, 4th was incomplete, I got a call for onsite interview.
Onsite interview initially consists of a Code Debugging round - you are given a C code of about 200-300 lines that has some intentionally made mistakes, you need to figure them out and make it run as expected. For me the question was to list all files and sub directories in a given path - 1. It should work for large directories such as /usr. 2. It had a memory corruption problem that would stop the program abruptly after some point of time. 3. It had a generic programming mistake due to which incorrect data/path was getting constructed. Tips: Be good with your C basics and pointer manipulations, malloc, realloc of 2d arrays etc, array of pointers, etc (I was expecting it to be a C++ question as the position was for a C++ Developer). I would not say the question was very difficult. Don't be surprised if you see a huge list of compilation errors in your initially run of the program - they would be simple. Code had 3 major bugs. I could resolve 2 (1 as expected, 2nd resolved the problem but not as per interviewer's expected fix), 3rd was memory corruption that I could not figure out and ran out of time), though the observer gave me like 4:00 hrs overall (ideally its a 3 hr test).
I think its a great place as far as the work is concerned, and quite a good culture as well, and quite a young workforce and a lively place. I was disappointed as I could not clear the debugging round.