The most romantically appealing concept to engineers designing distributed systems for the first time is "multi-region." Yet in practice, you quickly realize the hard truth: the moment data exists in multiple places simultaneously, everything becomes difficult. Clocks fall out of sync, networks break, transactions fragment. Leslie Lamport's 1980s observation becomes reality: "A distributed system is one in which the failure of a computer you didn't even know existed can render your computer unusable."