Notion's Seamless Database Cluster Expansion: Horizontally Scaling from 32 to 96 Databases

To handle rapid user growth, Notion horizontally scaled its database cluster from 32 to 96 databases. The post details the process, including choosing a data migration strategy, horizontally sharding both the databases and the connection pool (PgBouncer), data replication and validation, and the final seamless switchover. Through careful planning and execution, Notion successfully expanded its database cluster, increasing capacity and performance without any downtime, leaving ample room for future growth.