From a hardware point of view, this system is unlikely to exist, because you need a system with components that never have any reliability issues ever to have a

From a hardware point of view, this system is unlikely to exist, because you need a system with components that never have any reliability issues ever to have a totally deterministic system. From a software point of view, this system is unlikely to exist as it doesn't matter that the cause of your downtime is "something else that isn't our system". As a result, you're gonna end up requiring infinite reliable storage to upkeep your promises.