Inside Facebook Messages’ Application Server

This post details the internal architecture of the Facebook Messages application server, a dedicated system built to manage the infrastructure for Facebook Messages. It describes the business logic for creating, reading, deleting, and updating messages, including handling email, SMS, and chat integrations. Key technical aspects include the use of HBase for metadata storage with a denormalized schema for message threads, caching of user metadata using LRU caches to reduce HBase queries, and synchronization mechanisms to handle concurrent updates. It also covers the storage schema, metadata entities and indexes, action logs for state management and schema evolution, and real-time search indexing using Apache Lucene. The post highlights the use of dark launches for testing and validation.