First Tech Screening is leetcode medium and we need to compile and run and test. Second Tech Screening is a tree related problem I have never seen. With some hint, I was able to solve it. First onsite was a leetcode medium-hard one, but the interviewer gave it a different scenario and the problem was to implement an iterator out of it, different from the leetcode one. I did not resolve it timely. And he also asked me some C++ related questions, e.g. multithreading, and more specifically(atomic), which I also did not gave the ideal answer.(I believe there was some miscommunications and I did not get his point). The second one is also a leetcode style problem, string-related. Along with some project manage e.g. build/integration problems. The third one is all about C++, e.g. basic concepts of C++11 above, and some C++ basic concepts coding as well (compile and run). The fourth one is a fantastic one. It is the product manager round, we had a great discussion, related to OS concepts like process/thread/memory/cache, C++ related multithreading, project related, unit test, debugging skills etc.