Ex-Amazon here.

Leaked documents aren't necessary to know that Amazon — among other FAANG companies — stack rank. But I will say that when Forte (the system used for performance reviews) first rolled out about 4-5 years ago, it was initially intended as a way to solicit feedback from your peers: and it was used that way.

At first.

But of course, within a few years, the system evolved and was eventually tied to your compensation.