1. Recruiter call (phone)
2. Face-to-face video call with non-manager
3. The round (six back-to-back interviews)
Overall it was a negative experience, but I have some advice for others going into it.
First, push hard to talk to the hiring manager in the first few interviews. In mine, the manager was to be the first "face-to-face" interview (online), but they kept pushing and eventually they became the dead-last interview. This was NOT a good situation, because I didn't fully understand what they were looking for until the very last hour of 7 hours of interviewing.
Second, the person to impress is the "bar-raiser." There is one person who will ask questions like "how did you make X better" or "how did you go above and beyond?" I was very fatigued at this point and gave pretty limp answers for this.
Third, consider hiring a coach to train for the interview. I did for a future interview (not at Amazon) and they ripped my answers apart and gave me feedback. Best to be down a few hundred bucks and have a good-paying job than not to have one at all.
Fourth, be prepared for "technical issues." What I mean is that of my 7 interviews face-to-face, miraculously only one of them (the bar-raiser) had a working camera and the rest insisted that they had varying issues (bad camera, bad connection, and one outright said that they don't turn on video because of privacy)... but your camera is on by default. Take that as you want, as you can either elect to turn it off, or even call it out.
Fifth, take their 14 leadership principles seriously. They asked me 3 times specifically about which one speaks to me.
Finally, prepare a lot of stories. A bit of an annoying thing is that being asked similar questions for multiple hours, you're expected not to repeat relevant stories more than once or twice at most.
As for why it was negative, (1) my recruiter was haughty. His exact words when calling me to tell me I was rejected was "We spoke about you at length, and it's going to be a no." He then explained that they have high expectations at Amazon, implying fairly directly that I had not met them. I felt like I was just ejected from the "Mean Girls" table.
(2) cultural mismatch. Jeff Bezos (or rather just "Jeff") was brought up at least six times (no hyperbole), and his words and guidance treated like gospel. I have respect for him, but it felt outright surreal and sycophantic to talk with such reverence for a supreme leader not even in the room. While Facebook talks about "Mark" and Netflix talks about "Reed," it's not so aggressively in the forefront.