It's also not entirely static, there's a lot of checks in place because of licensing models, and beyond that there's different encoding and quality levels of streams to support various clients.
The AWS part is also very dynamic, at any given time most customers are (unknowingly/behind the scenes) participating in 8-10 beta features.
That said, this is all based on talks and presentations they have given at various conferences in the past. It could be different, especially some AWS parts.
You never notice all the times when the failover is executed smoothly with no interruption in service, just the times when something goes wrong.