Explanation
Why the waste happens and who it affects.
In non-production environments, a Multi-AZ DB instance deployment roughly doubles the cost of database instances and storage, and a Multi-AZ DB cluster runs three DB instances (one writer and two readers), with little added value. Unless explicitly required for high-availability testing, Multi-AZ in dev, staging, or test environments typically results in avoidable expense.
Billing model
The pricing dimensions that drive this cost.
RDS Multi-AZ instance deployments incur compute and storage charges for both the primary and the standby. Data transferred between Availability Zones for Multi-AZ replication is free.
How to detect
How to find it in your estate.
Identify RDS instances in non-production accounts or environments with Multi-AZ enabled Use environment tags or naming conventions to distinguish staging and development workloads Evaluate instance-level metrics to assess whether failover capabilities are actively used or needed Check for duplicated storage and compute resources across Availability Zones
How to fix
How to remove the waste.
Modify RDS instances in non-production environments to use single-AZ deployment Update provisioning templates and IaC modules to default to single-AZ for non-prod Create safeguards to prevent Multi-AZ deployments in dev/test unless explicitly approved
Documentation
Vendor references for pricing and configuration.