Migrating Messenger storage to optimize performance

What this post added

This post details the significant overhaul and modernization of Messenger's storage service to improve performance, efficiency, reliability, and ease of upgrades. Key contributions include the migration from HBase to MyRocks (integrating RocksDB as a MySQL storage engine) and from spinning disks to flash storage on Lightning Server SKUs. It also elaborates on the complex, two-phase migration process (normal and buffered flows) designed to handle over a billion users without disruption, including data schema redesign, invariant enforcement, and extensive data validation. The post highlights the resulting 90% reduction in storage consumption, 50x lower read latency, and enhanced disaster recovery automation.