cache coherency
Cache coherency is the incantation that promises to keep multiple processor caches singing in perfect harmony while secretly gnawing away at an engineer’s sanity. It vows that each CPU can hoard data independently but still pretend to speak with one voice when it counts. In reality, it spawns monstrous race conditions and drags developers into an endless debugging abyss. Decked out in elegant mathematics at conferences, it bewilderingly lures implementers into ritualistic procedures they never fully understand. It never works flawlessly across environments, dooming everyone to wander a labyrinth of parameter tweaks forever.