1. Phone interview asking general questions based on their tech stack.
2. On-site interview with the team lead asking in-depth questions based on their niche use of the technology.
3. On-site interview with VP R&D.
4. HR interview.
In my case, I was given the wrong subject and name of the interviewer. It seems like they messed up names who had interviews on the same time. I came completely unprepared. The company is too big for its own good.