Cloud cost
Committed use discount
A discount a provider gives in exchange for committing to a minimum spend or usage level for a fixed term.
Last updated
Definition
A committed use discount trades flexibility for a lower rate: you commit to a baseline of usage (or spend) for one to three years, and the provider prices that baseline well below its on-demand rate. Reserved instances and savings plans are AWS's two flavors of this idea; most major clouds offer some equivalent.
The risk isn't the discount. It's sizing it wrong: a commitment bought against last year's footprint can sit partially unused as workloads shift, which is why coverage and utilization need checking on a regular cadence, not just at purchase time.
Where it shows up
A committed use discount shows up as its own charge type on the bill: AWS Cost Explorer's Reservations and Savings Plans reports list it apart from the On Demand line for the same instance family. Azure and Google Cloud show the same split under their own commitment reports, keeping the discounted charge separate from pay-as-you-go usage.
What makes it expensive
A commitment sized to last year's footprint, then left unreviewed, is where the money goes. Workloads shift underneath it and the commitment does not follow. Coverage and utilization then drift in opposite directions, and neither moves back on its own. Put both reports on a fixed schedule and a stranded commitment surfaces while there is still term left to act on.
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- Idle and orphaned resources
- Storage class
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- Unit economics
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- Observability tax
- Metric cardinality
- High-water-mark billing
- Log ingest vs. index
- Snowflake credit
- Auto-suspend / resume minimum
- BigQuery slot
- Bytes scanned & partition pruning
- Time Travel & Fail-safe
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