How Uber Saved $6,000,000 in Database Costs

Uber reduced database costs by $6 million annually by migrating their financial transaction system from DynamoDB to DocStore, their custom MySQL-based distributed database. The migration involved building LedgerStore 2.0 with immutable records, data integrity guarantees, and solving hot partition problems through deterministic sharding. The process included careful data backfilling, shadow writes for real-time sync, and dual read validation to ensure zero downtime during the transition.