I can not go into the specifics of the questions because I signed an NDA but depending on which role you are applying for you should expect to get a bar raiser in that field. Amazon Cloud Support Field has disciplines in Networks, Analytics, Operating Systems etc. Also note that bar raiser questions can come from that field but also expect to know adequately enough in the other fields. Concerning your preference of Operating Systems, you can specify your preferred OS and they normally accommodate that. No need to dive into Linux if you are a Windows expert or vice-versa. I am sure you have heard of the Leadership Principles so make sure you have at least two examples per Leadership Principle. I would not advise memorizing them; I would highly recommend watching Dan Croitor's videos which explains and gives examples of how they would be phrased https://www.youtube.com/channel/UCw0uQHve23oMWgQcTTpgQsQ. In the On-Site interview, it is also discouraged to reuse the same examples for different interviewers; the reason is they consolidate their work and it shows you live out the principle if you have multiple examples. Glassdoor was very helpful in preparing for the interview as well.