Amazon engineer here! I love our culture of strong ownership and autonomy, and that we'll take risks, tolerate failures and give things around 7 years to mature and pay off. It's super rewarding to be able to own things and see them through, and to see things like AWS, Kindle and Alexa go big places. I've had my own projects work out and I've had things abandoned, and both experiences have been positive in the long run, if a little painful at the time.
As for the AWS thing ... I joined AWS pretty early in its history and even then we had amazon.com workloads and it was definitely the same infrastructure (data centers, network, operations, etc) as Amazon.com . My first two years I was writing code and building AWS services, while also supporting retail operations and dealing with the order pipeline - and I worked in Infrastructure; things were fairly integrated.