black board interview, the difficulty may be medium, will give hint if stucked. 2 interviewers at that time, final one is tech lead, surveillance team lead is terrible, quite picky

On-site technical interview and totally 5 stages. Back-to-back reviewed the resume and asked coding problems. Didn't required to write a perfectly correct code on the white board, but at least to give an answer with the best complexity. I failed at stage #2.