Round1:
Q1. To my surprise the first round was a design round where I was asked to design a system that could send email notifications in bulk. Focus was primarily on failure scenarios and handling.

Round2:
It was a coding round and I was asked two questions.
Q1. In a stream of characters return the first non-repeating character.
Q2. Join the nodes of the same level using a next pointer.

Both qiestions needed be solved and coded within one hour

Round3:
It is also a coding round just like round 2.
Q1. Find the maximum in sliding window.
Q2. Straight forward- topological sorting question.

Again, both question needed be solved and coded within one hour.

I was able to solve all four questions of coding round, although the design round was average. I was expecting that I will get another opportunity in BR round but I didn't get the opportunity.

Also, each and every round had multiple questions from Amazon's principles and behavioural part. These questions needed a specific scenario to be described that actually shows the aplication of the principle. Any answer that is not specific won't be accepted.

Hopefully this will help other candidates while preparing. I wish you luck.