EC2 RI Optimizer: Warning message "Savings Plan purchases made within the selected evaluation period are not accounted for in the recommendations"

Products

• CloudHealth

Issue/Introduction

On EC2 RI Optimizer, the user is getting the following warning

We’ve detected a Savings Plan in your AWS Cost and Usage Report (CUR). Savings Plan purchases made within the selected evaluation period are not accounted for in the recommendations. For more information, please see the FAQ in the Help Center.

 

Resolution

This warning message provides information on how newly purchased SP may impact the EC2 RI Optimizer based on the Time Period. To analyze

Summary: If a customer lacked a Savings Plan (SP) for the first 20 days of a lookback period and only purchased one on the 21st day, the resulting RI recommendations may be higher than expected.

The Reason: The RI optimizer calculates recommendations based on remaining on-demand costs. Since an SP covers a portion of those costs, its absence during the first 20 days results in higher on-demand figures. Consequently, the tool may recommend a larger RI quantity than the customer actually needs for their current "post-SP" environment, triggering the warning

Example: When analyzing a 30-day window (e.g., Jan 16 – Feb 15) where an SP was purchased mid-month on Feb 1st, the recommendations may be inflated. The system factors in the 15 days of full On-Demand usage prior to the SP purchase. Since your current On-Demand exposure is now lower, following a 30-day recommendation could lead to over-purchasing.