EC2 Low Risk Rightsize

Opportunity Name:

EC2 Low Risk Rightsize

AWS Resource Type:


Opportunity Description:

AWS Compute Optimizer automatically provides EC2 instance right-sizing recommendations to save costs but does not provide a way to realize the savings at a scale. CloudFix builds on Compute Optimizer recommendations by filtering opportunities, executing changes automatically, and monitoring performance to prevent degradation. These recommendations don't include changes to a different processor family (e.g. Intel to Graviton) which is done by other FFs.

Criteria for identifying the opportunity:

This FF excludes recommendations involving: 

  • Instances in ASG/EMR as they are constantly provisioned and decommissioned
  • Instances without support for Elastic Network Adapter (ENA)
  • AWS Marketplace/DevPay instances
  • Rightsizing to nano or micro instances as previous executions proved to cause issues
  • Platform differences as these may entail driver updates or /etc/fstab modification
  • High-risk changes (e.g., across family types)

In addition, the FF will use a longer lookback period if the customer enables this. 

Potential savings (range in % on annual basis):

Compute Optimizer's cost savings estimates are based only on on-demand costs, which can be inaccurate for big customers with different pricing structures. To provide a more accurate estimate, this FF computes savings as a percentage based on the relative power of the source and target instance types. Maximum potential savings are estimated to be around 40%. 

What happens when the Fixer is executed?

The instance is stopped, retyped, and then restarted.

Is it possible to rollback once CloudFix implements the fixer?

Yes, the instances are continuously monitored for 30 days following a downsizing. They are automatically rolled back if the instance maxes out CPU or memory for an extended period or does not restart after retyping.

Can CloudFix implement the fix automatically once I accept the recommendation?


Does this fix require downtime?

Yes. The EC2 instance is stopped and started.

Note that when an instance is stopped, the public IPv4 address that Amazon EC2 automatically assigned to the instance on launch or start is lost. To retain a public IPv4 address that never changes, you can associate an Elastic IP address with your instance.

More information on what happens when an instance is stopped and started


Additional Resources:

CloudFix Knowledge Base



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