Amazon Lab126 Engineering Manager interview questions

A chaotic process overall. All interviews begin with "tell me about a time..." questions, with copious note-taking (documenting meetings is one of Amazon's principles). I interviewed with several engineering managers and a few senior/principal engineers. I had been interviewing with many other companies the same week, and a few differences immediately struck me: Although the interview did not have a dress code, everyone, even the engineers, was dressed up. Even the engineers show up to work in business casual. The engineers, even the principals, were either faking vapidity to try and draw answers out of me or were some of the dumbest I've ever seen in the tech industry. I had to explain aspects of architectural and coding answers 3/4/5 times, because they simply didn't get it. They asked me the complexity of a couple of "for i from 0 to n; for j from 0 to i" loops, and couldn't wrap their heads around the fact that 1+2+3+... = n*(n+1) / 2 was O(n^2). They would constantly ask me "does this work?", I'd step through it line by line to show them that the algorithm does in fact produce the right answer, and they'd continue just sitting there looking puzzled. One engineer asked me to explain polymorphism to him; it baffled him that you could store derived class objects in an array. These were Principal Engineers! The managers seemed much sharper. Unfortunately, they were largely bound to structured questions to try and ferret out Amazon's canned "values", and only occasionally deviated to touch on actual management ability. I had to submit a two page essay before the onsite. I don't think anyone actually read it. It never came up again once I submitted it. No lunch, no drinks, no snacks. I was very hungry by the end of the day, and was told I could purchase something from a vending machine outside. Overall, I came away with the impression that Amazon was stuck in the 1980s when tech companies didn't have to compete with each other for workers and that this was probably the explanation for why their engineers were so subpar.