How we migrated 150 Cloud SQL instances using GCP DMS

This post details the migration of 150 Cloud SQL instances from MySQL 5 to MySQL 8 using GCP DMS. It highlights the motivation for the upgrade (JSON improvements in MySQL 8), the main challenges (data copying, source DB availability, service restarts/redeploys), and the solution implemented: GCP DMS with continuous migration jobs. A key contribution is the development of an Asynchronous Upgrade Framework, a state machine stored in GCS, to manage large-scale, long-duration upgrades. The framework ensures idempotent operations and handles state transitions based on replication lag and system load. Early performance gains with MySQL 8 are also noted, including improved CPU utilization and reduced disk I/O.