It's always East 1... Jokes aside I don't understand how often east-1 is taken down compared to other regions. Like it should be pretty similar to other regions architecture wise.
Isn't east one the "core" datacenter and also the oldest? I'd imagine it has more load than the other regions and also has more tech debt and architectural / engineering debt because they had less experience when they built it.
Also iirc some services rely on east-1 as a single point of failure for configuration (like IAM or some S3 stuff?)
