Cloud Database Cost Optimization: RDS, Cloud SQL, and Cosmos DB Compared

Compute costs are visible and easy to reason about: vCPUs times hours times price. Database costs are different. Each managed database platform has its own pricing model with its own hidden multipliers, and the levers that reduce cost on RDS have almost nothing to do with the levers that reduce cost on Cosmos DB. Most teams approach database cost optimization by right-sizing instances. That helps, but it is rarely the biggest lever. The bigger problems are structural: Multi-AZ enabled on databases that never need failover, non-production databases running at 3am on a Sunday, Cosmos DB containers provisioned for anticipated peak load that arrived six months ago and left, Cloud SQL storage that grew automatically and can never shrink. This piece covers where the money actually goes on each platform, and the specific changes that reduce it. Why Database Bills Are Harder to Optimize Than Compute Compute instance costs are transparent. Database costs have multipliers embedded in the pricing