The Anatomy of a Zero-Downtime Database Migration

Database migrations are notoriously stressful. Taking the system offline was not an option for our enterprise customers. We utilized a rigorous multi-phase strategy.

Dual Writes and Backfilling

We spun up the new database, implemented dual-writes on the application layer, and slowly backfilled the historical data in the background. Once parity was mathematically verified, we flipped the read traffic entirely without users noticing a microsecond of downtime.