[bvaldivielso]

The article mentions the software running in each availability zone as a source of correlation in the system. That correlation can be bad, because it makes the system less resilient (that's the point of the article).

I wonder if Amazon would ever consider having completely independent implementations of the same software (made and maintained by different teams) running in each availability zone. This would reduce the correlation between AZs. Of course, this would be much more expensive, but perhaps worth it if availability was critical.

In fact, I vaguely recall that this was a common practice in the development of some kind of critical system (avionics?).