Building Facebook Messenger

This post details the technical challenges and solutions involved in building Facebook Messenger as a standalone application. Key contributions include the adoption of MQTT for persistent, low-latency mobile connections to reduce message delivery time from seconds to hundreds of milliseconds, and the integration of different communication channels (chat, text, email) to create a seamless user experience. It also highlights the challenges of adapting to the existing Facebook Messages infrastructure and making product decisions around communication channel integration.