By the time you finish reading this, someone at Wix is probably in the middle of a data migration. We've run migrations that lasted anywhere from a few months to two years. More recently, we've completed large and complex migrations in a few weeks. The difference wasn't the tooling, which barely changed. It was that we had finally learned which problems show up in every migration, and started dealing with them before the migration began instead of in the middle of it. Recap:

The Challenge At Wix, multiple applications share the same DB cluster. The reasons vary: consolidating apps from the same domain, grouping several small apps that don’t justify a dedicated cluster, or simply optimizing cost and operational overhead. However, this setup comes with a significant risk: every application on the cluster has the potential to impact all the others. One real example: we had a critical service related to user authentication sharing a DB cluster with s