> Both Google and Amazon use stack ranking, which is about the most brutal system there is.
This isn't really true (at least at Google, IDK about Amazon). "Stack ranking" historically has two components:
1. Being rated relative to your peers as opposed to a rubric.
2. (Usually fast) removal of the lowest performing individuals.
When combined, these become "fire and replace the bottom 3% of people on every team every year." The downsides to this approach are that if you're on a strong team, you may be a median employee, but be the weakest on your team, and be forced out for this reason. It's clearly problematic.
IDK about amazon, but the first is only half present at Google, and the second isn't really at all.
In some sense you are rated to your peers, not a rubric. But only in the sense of at aggregate (that is, in an organization of 1000 people, you'd expect ~30 people to be in the "worst 3%" category, so if only 10 are, that may raise some questions.) This removes the competition and potential animosity with your direct peers and aligns more with the rubric based idea, though it is possible that a an organization may have across the board above-average (or below) performance on occasion.
For the second, people with NI ratings aren't immediately fired (I know of a few people who got NI and found new teams and much more happiness), though obviously consistent NI could result in that.