Amazon Software Development Engineer interview questions

I had had two phone screen interviews before I went to Seattle for my onsite interview. The phone interviews were 45 minutes each and the onsite interview had 5 rounds, each about 50 minutes. It seemed that amazon was lack of software engineers because I had seen a lot of candidates. In onsite interview, I was staying in a conference room for one day except for a lunch interview. The interviewers came to the conference according to the schedule. It was a fantastic experience but I didn't not get an offer.