I applied online and was contacted for a HR screening where they asked basic questions about why I wanted to work at amazon and took the opportunity to tell me more about the company. Then, I had a series of two 30 minute phone interviews with engineers where they asked me to solve some algorithmic questions. I was able to solve 3 of the four questions they asked. Apparently they each vote up or down and on a split, you have a third interview. I guess my answers were good enough because I didn't have another one.