So it is both available and consistent (but perhaps only in read your own writes way?). What is then with resilence to network partitions, referring to CAP theorm? Did they build super reliable global network, so this is never a real issue?
From what I've read, if a network issue occurs which would impair consistency, S3 sacrifices availability. The write would just fail.
But this isn't your 5-node distributed system. Like they mention in the article, the witness system can remove and add nodes very quickly and it's highly redundant. A network issue that would actually cause split-brain or make it difficult to reach consensus would be few and far between.