I applied through an employee referral. About a month later, I actually started the interview process. The first round was an online coding/debugging challenge followed by a logic challenge. You can't really study for these; if you've passed an intro to programming class you will pass this. One day after I took the debugging challenge, I got a link to the second round online challenge. These were two questions similar to what you might see on Hackerrank or Leetcode. The first question was around an easy/medium, and the second one was, in my opinion, a hard. I kind of froze when I couldn't think of a solution for the second question, and I actually ended up literally having no code on it. I chalked that up to a failure, and moved on. A week later, I was surprised to see that I had moved on to the final round, which was a virtual interview using Amazon's internal online meeting app. The interview consisted of introductions and details about my resume, followed by some basic questions on certain data structures, followed by one medium difficulty programming challenge. This interview went much more smoothly than the first one, and I left feeling confidant. 4 days later, I got the offer.