I interviewed 3 times with Amazon before I got an offer from them. And then when I was there, I kicked ass. There's little correlation between the interviews and how good you actually are. Also, while I was at Amazon, I did probably over a hundred interviews (in person and phone screens). Interviewing in hard and there are a lot of very bad interviewers there. They try to keep a similar bar across the company, but I found it to be very inconsistent from team to team. AWS tends to be one of the harder teams to interview for.