There were 3 rounds: first round was multiple choice reasoning test (~30mins) along with 7 debugging questions (21mins given). Second round was 2 programming questions. Third was phone interview over an online editor. The first test is autograded so you know pretty quickly if you've advanced. I didn't like how I asked to reschedule my interview and was ignored. I also did not like how Amazon doesn't consider culture fit, meaning they hire almost solely on technical ability rather than being a good team member/person to work with. I'm glad I'm going to be working at one of their subsidiaries with a more employee-friendly culture.