Both ELB and RDS only work within a single zone, and this latest incident occurred in "multiple availability zones", according to Amazon ELB and RDS work acros

Both ELB and RDS only work within a single zone, and this latest incident occurred in "multiple availability zones", according to Amazon ELB and RDS work across multiple zones. So a single ELB can span EC2 instances in multiple zones within a region. So I could have 4 EC2 instances in us-east-1a, us-east-1b, us-east-1c, and us-east-1d, with an RDS instance in us-east-1a and a read replica in us-east-1b. What happens when us-east-1a goes down and every big user in that AZ has failover mechanisms that start moving instances, EBS volumes, RDS databases, S3 buckets and who knows what else from us-east-1a to us-east-1b,c, and d? Those AZ's get overloaded, API endpoints get slammed, and the whole region goes down in flames. It didn't matter that these availability zones are hosted on separate infrastructures (from what I gather, the zones are separate datacenters in the same city with low latency connections between them, but separate power sources and backbone connections). Meanwhile, all's quiet on the US-West front. That's what got me thinking about failover across regions.