I was contacted through LinkedIn by the AWS Mobile division, as I had stated in my profile that I had been developing SDKs for mobile applications. The whole process lasted two months and Amazon HR were extremely helpful and straightforward throughout.
The first steps were a couple of Skype interviews and a CV profiling, which took a week. After that, they announced they were going on a recruiting trip to Barcelona, in the same dates as the Mobile World Congress. They offered to pay for all expenses, including plane, taxi and hotel, so I could make it to Barcelona for the personal interviews.
Personal interviews were at the same time interesting and puzzling. They set up shop in a touristic apartment building, and interviewed 4 candidates each morning. Each candidate was shown a room and stayed there while the interviewers were rotating. Interview slasted one hour and were half technical (simple problem resolution) and half personal (predefined questions and general chatting). The technical part was quite easy: pen and paper exercises writing algorightms for tree traversing, sorting, parsing HTML, and such. Interviewers were specially interested in knowing the order of magnitude of my solutions and if I could devise some ways to optimize them without the limitations of a pen and paper test.
On the other hand, the personal questions were a stopper. For starters, the interviewers were developers just like me, not HR people and not even managers. They weren't used to asking those kind of questions and it showed, as they were unable to get the conversation going if I stumbled finding an answer or simply understanding the question. That was a bummer, because once we put aside the standard questions and started chatting about what they did in Amazon, and more technical details, it was really fun and interesting. Personal questions didn't allow me to speak about myself in a freely manner, so I had to use those 15 minutes between interviews to pass along some tips about my strong points.
The standard personal questions they had to ask (and write down the answers, as they really didn't have the means, nor the interest of expanding on them) were all of the kind: "Tell me about a past experience where you... resolved a conflict with a teammate | provided value for a client | had to deal with a deadline you couldn't meet ...". Those questions were really exhausting, because I had first to understand what they were really asking and what kind of answer was expected. Then, to navigate through my memory to find a suitable experience to tell. And finally, translate it to comprehensible terms, which in the case of a developer often implies a lot of technical context sure to be lost in the transcription. Worst of all, there wasn't any of the more usual questions like "things you do well, things you must improve, what do you want to do in the future, etc." that you may have rehearsed.
I was told I would receive an answer after a week, but I didn't. I kept asking by e-mail each week, and always told I was still in the process and a decision had not been made yet. After more than three weeks I was finally told the positions had been covered by other candidates. I reckon I was being kept as a replacement in case some of them didn't accept their offer.