I had almost exactly this same engineering test when google interviewed me in 2006. It was terrible, and left a bad taste in my mouth. Given the complexity of the work I was doing at the time, the entire thing seemed ridiculous.
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Recruiter: "I was looking for you to say it's a fingerprint"
So I guess I was wrong, because despite explaining them in decent detail, I didn't use the one keyword.
Oh well.
I cannot obviously tell you the exact specifics because of the NDA.
Maybe I dodged a bullet there and Amazon would have been a bad place to end up anyway.