“The new service, built in-house and later open-sourced, was more scalable and improved the accuracy of timekeeping in the Facebook infrastructure from 10 milliseconds to 100 microseconds.”
Off-the-shelf time servers run closed software and break in ways you can’t fix yourself. One bad part means shipping the box back or buying a new one. Facebook built a PCIe card that turns a regular server into a time appliance and published the schematics. Anyone can now build one for a fraction of the price. The vendors’ markup was the first casualty.