Barring the specifics, we deploy new machines in batches of tens of thousands at a time and they practically don't receive any production traffic for weeks while repeatedly running burn-in tests followed by baseline daemons. If they survive, they get provisioned for production.

Infant mortality rate of CPUs--especially single socket designs--is very low compared to DIMMs and SSDs. They tend to develop these issues later in their economic lives. They are also comparatively rare to other module failures.