VM Right-sizing (GCP)
CostLens surfaces Compute Engine machine-type recommendations to move over-provisioned VMs to a smaller, cheaper machine type — and can apply the resize for you.
CostLens surfaces machine-type recommendations from Google's Machine-Type Recommender — suggestions to move an over-provisioned VM to a smaller, cheaper machine type based on observed utilisation. Over-provisioned VMs pay for cores and memory they never use.
How it works
Recommender analyses utilisation
Google evaluates CPU and memory usage and suggests a right-sized machine type per instance.
CostLens reads them read-only
Using the recommender.viewer + Compute read scopes from GCP Accounts, CostLens ingests each recommendation and its projected saving.
Severity and savings are assigned
Savings come from the Recommender's costProjection, normalised to a 30-day month.
What to do
- Review the current vs recommended machine type and the projected saving.
- Confirm the smaller type meets your peak requirements (headroom for spikes).
- On Apply, choose either the CostLens-recommended machine type or a different type from the size picker — you keep full control over the final size. CostLens stops the instance, changes the machine type, and starts it again (GCP requires a stop to resize).
- The change is reversible within 24 hours.
Test first
If the workload also runs in a non-production project, apply the resize there first to confirm no performance regression before touching production.
Severity levels
| Severity | Estimated monthly savings |
|---|---|
| critical | >$500 |
| high | $100–$500 |
| medium | $20–$100 |
| low | <$20 |
Required permissions
- Detect:
roles/recommender.viewer+ Compute read — see GCP Accounts. - Apply: Compute write covering
compute.instances.setMachineType,compute.instances.stop, andcompute.instances.start(granted by the CostLens write role when Auto-Fix / apply is enabled).
Limitations
- Recommendations are based on Google's observation window; instances with variable or seasonal load may need judgement before resizing.
- Right-sizing requires a stop/start, causing a brief interruption — schedule during a maintenance window.