This holds up to a point. The systems that require really little downtime get progressively more complex. Need to handle machine failures? Push a bugfix withou

This holds up to a point. The systems that require really little downtime get progressively more complex. Need to handle machine failures? Push a bugfix without causing downtime? Maintain a single state across the redundant machines? Handle load spikes? Ones created on purpose to DOS you? All of this requires additional mechanisms, which can themselves cause failures.