Building a more accurate time service at Facebook scale

What this post added

This post details Meta's migration from ntpd to chrony for its internal NTP service, achieving accuracy improvements from ~10ms to microseconds. It describes the four-strata architecture of their NTP service, including the use of atomic clocks and GNSS. The post also covers the challenges of time synchronization at scale, the limitations of daemon estimates, and the validation of accuracy using 1PPS signals and specialized hardware. Finally, it announces the open-sourcing of their NTP libraries.