Does anyone know how often an AZ experiences an issue as compared to an entire region? AWS sells the redundancy of AZs pretty heavily, but it seems like a lot of the issues that happen end up being region-wide. I'm struggling to understand whether I should be replicating our service across regions or whether the AZ redundancy within a region is sufficient.
The main issue tends to be a lot of AWS internal components tend to be in us-east-1; it’s also the oldest zone. So when failures happen in that region (and they happen more commonly than others due to age, scale, complexity) then they can be globally impacting.
Availability zones are supposed to be another fault boundary, and things are generally pretty solid, but every so often problems spill over when they shouldn't.
The general impression I get is that us-east-1's issues tend to stem from it being singularly huge.
(Source: Work at AWS.)