The process took 1 day. I interviewed at Amazon in Mar 2012
Interview
It's a hiring even in Seattle. The onsite interview had 5 rounds, all of them are technical questions, you need to explain you idea and also write the proper code on the wall. Most of the questions are algorithm and data structure related, if you've reviewed all these questions in the Amazon forum, you should be OK.
Interview questions [1]
Question 1
have 1 million product id, get the top 10 in the past 1 hour