Facebook recently ran an experiment. Inside a test lab, somewhere behind the scenes at the world’s most popular network, engineers sidled up to a computer server loaded with software that typically drives the Facebook website and started messing with the CPU.

Every processor includes something called a cache — a place to temporarily store data without sending it all the way back to a machine’s main memory — and with their test machine, these Facebook engineers started shutting down portions of the cache, just to see how their software would respond.