Have you tried artificially taking out US-EAST in production?
I haven't but I know that it'd fail. We'd continue serving up the static content just fine, until it got evicted from the CDN cache. We basically need to implement two things here:
Some smarts on the client to initiate some sort of fallback API that it can use, if the page has already located successfully
Some smarts on the CDN to failover to the other region
From the tech-review