Qualifier - This review is for Amazon Web Services only.
If i had to pick one word to describe their process, it would simply be difficult. My first observation - They have a stable of recruiters and HR specialists you will engage with, but none of them are assigned to a region, functional skill, or segment. It is also not clear which of them has "responsibility" for the process. The second issue is that the well advertised culture issues are very real, but their employees can't see them. The level of arrogance and elitism during the process was genuinely disappointing. They spend a lot of time telling you about the Amazon culture and the leadership principles during the process (and how special they are), but they seem to forget that candidates are also evaluating whether AWS is actually a good place to work. They also completely disregard the recent New York Times article about their culture issues which seem relevant to my experience as well.
The process itself is pretty standard. Initial interview with HR screener, interview with a HR scheduler, 1st call with hiring manager or lead, second interview with HR screener, then a 1/2 to 3/4 day onsite interview panel of 4-6 people. It is also important to note that the hiring manager doesn't have any real authority in the hiring process. FYI - you have to gain consensus from all the people you meet with (not sure about the ratios, they wouldn't share any details on this), and the manager is only one vote in this. I would suggest bringing food and drink with you, and be forewarned that "bio" breaks are minimal, if you get them. You will either have to do a presentation on a topic of your choice or provide a writing sample of 1-4 pages on a topic they will provide you. You will not receive any feedback on either of these afterwards. They will not tell you who you are meeting with in advance, nor did most of the interview panel people introduce themselves before jumping into their battery of questions. Be forewarned, AWS is real big on data entry, and the people in the room will spend a large portion of their time entering notes into the HR system during the process. This is a another area that they could improve on as it's not very personal (which is a consistent theme with them it seems). The only highlight of the process is that they are very quick to let you know whether or not you got the job or not, usually within a day or two. However, they again will not provide you with any feedback on gaps if you have them so you can improve if you wanted to come back and try again later.
With the incredible growth of AWS, their interview process is likely going to have to change if they want to attract high quality candidates. It's also reasonable to assume that as they grow and need to add talent, that they are going to have to soften some of these rough edges at the expense of their "culture". If you can't convince potential employees that AWS values your potential and that the culture is great, they will continue to struggle to attract talent. This process likely works well in geographies with limited employment options, but in the Silicon Valley Google and Microsoft are right down the street, and hiring as well.
Hope this helps others have a better experience than i did.