AWS bill line item
Multi-AZUsage:db.m5.large
The hourly compute charge for a Multi-AZ RDS deployment, which bills for both the primary instance and its synchronous standby replica in another Availability Zone.
RDS Multi-AZ instance hours
Verified against official AWS documentation last checked
Why it shows up
AWS's own documentation notes Multi-AZ deployments can cost roughly twice as much as single-AZ, because you're billed for two full instances (plus duplicated storage) instead of one. This routinely surprises teams who enabled it for durability without budgeting for the doubling.
It appears as a separate usage type from plain instance hours, so cost reports that group only by instance type can hide it under an unexpected bucket unless grouped by usage type instead.
How to cut it
- Confirm Multi-AZ is required for each database's durability/availability target before enabling it.
- Use Multi-AZ only for production; keep dev/staging/QA databases single-AZ.
- Apply commitment discounts: Multi-AZ standby instances qualify for the same discounts as primaries.
- Consider a distributed-storage engine (no separate standby-instance charge) as a lower-cost HA alternative for some workloads.
How to read this code
:instanceType suffixThe specific instance type or size a charge applies to, e.g. BoxUsage:m5.large. One line per distinct type in use.
Source
Source: AWS docs →Found Multi-AZUsage:db.m5.large on your own bill?
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