That's the problem. As a designer your goal is not to claim that you can design unflawed system. Instead it is to use all your humility (and skills) to design s

That's the problem. As a designer your goal is not to claim that you can design unflawed system. Instead it is to use all your humility (and skills) to design stuff that are simple enough that are unlikely to fail because the complexity level reaches the limit of prevention and ability to analyze the failure modes. I would like to know how much of the design in places like AWS is made more complex by the requirements of HA itself, but my guess is, a lot.