I've heard from a very reliable source that internal to Amazon they are still stack ranking employees; despite an article from a couple of years ago where they publicly said that they were no longer doing this. Everyone in the company is judged as either TT (top tier), HV (High value) or LE (Least effective). If you are graded as an LE; you'll be forced into a plan which likely ends with your departure from the company.
Not only that; management sets quotas for the number of folks that they need to be LE; essentially driving out 5-10% of the company; potentially creating a toxic work culture. Some groups know this and others do not; but it sounds like this is happening across the board. "Buyer Beware" to folks applying there; you may want to take this into consideration before stepping into such an environment.