Building a more accurate time service at Facebook scale

This post details the evolution of Facebook's time synchronization service, moving from ntpd to chrony to achieve sub-millisecond precision. It describes the four-layer NTP service architecture, the comparison of ntpd and chrony's accuracy and resource consumption, and the validation of chrony's performance using 1PPS measurements in a timing laboratory. The post also announces the open-sourcing of Facebook's NTP libraries.