AWS / Technical guide
Right-size EC2 against the workload's limiting resource
Low EC2 CPU utilization can coexist with a memory-bound cache, an EBS throughput bottleneck or a network-intensive service. Reducing the instance size can remove the resource the application actually needs.
A defensible resize candidate names the target instance type, the constraints it must preserve and the test that will validate it. A utilization threshold or percentage estimate alone cannot establish those facts.
Discuss AWS rightsizing scopeCheck the constraints a smaller instance changes
Review CPU demand and peaks alongside memory pressure, swap, EBS throughput/IOPS, packet rate and network bandwidth. Burstable families also require attention to CPU credit behavior. A smaller instance may change several ceilings at once.
An architecture change to Graviton requires compatible software, images and dependencies. Local instance-store availability, hypervisor and network-driver differences can also affect a migration. Treat an instance-family change as an engineering proposal, not a price-only substitution.
| Constraint | Review |
|---|---|
| Memory | Peak working set, cache demand, swap and missing instrumentation |
| CPU | Representative peaks, workload cycles and credit behavior |
| EBS | Instance and volume throughput/IOPS ceilings |
| Network | Bandwidth, packet rate and latency under load |
| Compatibility | CPU architecture, drivers, local storage and regional availability |
Use a window that contains the business cycle
A short observation window can miss month-end batch processing, seasonal demand or a recent deployment. Inspect the maximum and percentile behavior as well as the average. Include the owner in choosing how much historical evidence is representative.
AWS Compute Optimizer documents a default 14-day EC2 analysis window and a longer-window paid option. Memory analysis requires appropriate agent instrumentation. Its performance-risk and target-type information should be examined with the application's own service indicators.
Compare the effective cost of the combined workload
Estimate the target's charges for the same runtime and purchasing assumptions. Review Savings Plans, Reserved Instances and any dependent storage/network costs. Lower on-demand list price does not necessarily reduce current commitment payments.
If you plan to change both size and runtime, calculate one combined scenario. Adding a full scheduling estimate to a full resize estimate can count the same avoided usage twice.
Select and test
Choose a compatible target and validate application performance in a safe environment.
Define rollback
Agree thresholds for latency, errors, capacity pressure and restart recovery.
Observe the result
Compare post-change health and suitable billed periods with the original estimate.
What Costframe's AWS pilot signal means
The implemented EC2 pilot path uses CPU-led low-utilization review over a labelled 14-day window. Its oversized-instance financial estimate uses an explicit policy percentage, not a fully modeled target-SKU replacement. Memory utilization is not analyzed in that path.
Those limits should prompt additional engineering evidence. Costframe does not claim to replace Compute Optimizer's target-type modeling, perform an automatic resize, or certify realized savings from a finding alone. AWS pilot coverage must be confirmed for your account and resource scope.
References and further reading
Provider documentation explains native capabilities. Costframe availability and limitations are stated separately in this guide.
Check the pilot evidence you would receive
Ask which EC2 metrics, cost sources and account scopes are supported before making a rightsizing decision.
Discuss AWS rightsizing scope