Realized Savings can be calculated using FlexReports. The below example details the process that can be used to calculate this metric:
In this example, we are looking to understand how much savings we're getting from purchasing Redshift reservations.
We will use the combination of UnblendedCost and reservation EffectiveCost to get the complete Redshift cost. June 6 UnblendedCost is $42.67, and reservation EffectiveCost is $91.22, with the total of these two figures being $133.89:
To understand the savings from using the reservation we will take the value of $133.89 and subtract it from publicOnDemandCost column in the FlexReport of $172.99 to get a realized savings of $39.10: