First stage is the jam round where you have to speak for a minute about any topic. Don't mug up something, speak fluently and confidently.
Then you have the versant test and Watson test.
Last round is the operational round where you'll be interviewed by a couple of managers. The managers who interviewed me were very chill and didn't give me a tough time.
HR at Amazon is probably the worst you'll experience, just be ready for them, the are too uptight, rude and don't bother about your experience. Interview process is tedious, they'll make you wait for hours between two rounds.