[ObviousScience]

This is simply a perspective on systems engineering.

My argument would be that part of the system is always down, the question is which part and how long, and how that impacts the system performance on the whole.

AWS services work well if you build a stateless system which is in some senses "embarrassingly parallelizable", because you can talk about the capacity of such a system, and the impact of non-functioning components is easy to predict. This is how most standard engineering is done, across disciplines.

Traditionally, it has not been the case in computer systems, but most modern techniques advocate using such systems, because they're MUCH more reliable.

You just sound like you need a safety blanket for emotional reasons, not that you're making sound engineering points about how to most cheaply engineer a high availability system.

I mean, do you really believe AWS engineers aren't working hard to keep their system fully functional?