Applied directly through Amazon website, was offered phone screen interview, completed numeracy test, then offered in-person interview, received phone call 5 working days later notifying me of decision. Total process took about 4 weeks start-to-finish.
The phone interview will be about 30-40 minutes long and will follow the STAR (Situation, Task, Action, Result) format and questions asked will be nominally based on the 14 Amazon 'Leadership Principles'. You'll receive a .pdf via email explaining what these are if you're not familiar.
The in-person interview will be 3 x 45 minute interviews, each with a different person on the team. It will follow the same format as the phone interview, just slightly longer and more in-depth. In fact in my case, one of the interviewers was actually the same person who did my phone interview.
I then received the call notifying me of their decision, which was a no. I tried to ask for feedback, but they were intentionally vague and wouldn't explain their decision. But then they told me they wanted to pass on my details to another department as they thought I'd be suited to a Business or Finance Analyst role.
From this, I can only surmise that I performed okay on the interview and leadership principles, but that my experience is not suitable or sufficient for this role. As they refuse to actually explain their decision (the phone call lasted about a minute or two, tops), it's hard to feel positive about the experience, especially given the effort they expect applicants to put into learning their interview format. Also, I haven't received another call from Amazon regarding the other role, so I don't know if what I was told was genuine or not.