Faster backups with sharding

This post details how PlanetScale leverages Vitess sharding to dramatically speed up database backups. It explains the internal backup process, including restoring previous backups, catching up changes, and storing new full backups. The core contribution is demonstrating how parallelizing these steps across shards, rather than performing them serially on a single instance, reduces backup times from hours/days to minutes/hours for large databases. It also discusses the trade-off of replicating catch-up changes from the primary versus a replica.