Live Commenting: Behind the Scenes

This post details the engineering challenges and solutions for implementing 'live commenting' on Facebook. It describes the shift from a polling-based approach to a push-based system to achieve real-time communication. Key technical contributions include the design of a system to track viewer-to-content associations at scale (16 million new associations per second) and the adoption of a "write locally, read globally" storage strategy to manage high write loads and reduce cross-country bandwidth usage.