I understand that us-east is AWS's oldest and biggest facility, but Amazon seems to have more money than Croesus, why aren't they fixing/rebuilding/replacing us-east with something more modern?
us-east is a geographic distinction within which there are multiple regions. us-east-1 and us-east-2 are not the same. This outage occurred in us-east-2. Within an AWS region there are multiple data centers. They call their data centers availability zones. The availability zone AZ1 was the one impacted, and within that availability zone, most likely only a subset of servers.
us-east-1 is the region you're thinking of that has issues. Mostly due to being the largest region (I think?) and like you mentioned, the oldest.
My first instinct would be to guess that something like this happened because of some intentional and well-meaning effort to upgrade some critical part of their infrastructure. Just my hunch given that it happened during the middle of the week in the middle of the day, and came back relatively quickly. The quick but not instantaneous bounce back has the hallmark of someone following a carefully laid out worst case contingency plan. I look forward to the postmortem.
