RDS Aurora MySQL Reserved Instances

Hi,

Aurora MySQL Reserved instances are size flexible within the instance family. Size-flexible reserved DB instances are available for the following Aurora database engines:

• Aurora MySQL
• Aurora PostgreSQL

You can refer to the below documentation and compare usage for different reserved DB instance sizes by using normalized units per hour. https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/USER_WorkingWithReservedDBInstances.html#USER_WorkingWithReservedDBInstances.Overview

Reserved instance db.r6g.4xlarge will have billing benefit applied to 50 percent of the usage of the DB instance db.r6g.8xlarge. Reserved Instances provide a billing discount compared to On-Demand pricing, but you are charged for the entire term of the Reserved Instance regardless of whether the associated RDS instance is running or stopped.

For Reserved Instance billing, running DB instance usage is first compared to your active Reserved Instances at each hour. If the amount of running instances is less than or equal to the total Reserved Instances you have purchased, all running DB instances will be charged at the Reserved Instance rate per each hour. Any usage of running DB instances that exceeds the amount of applicable Reserved Instances you have purchased will be charged the On-Demand rate each hour.

Please refer to the link for more details regarding how billing works for RIs

• How Billing Works

Billing is calculated at hourly basis and had to be continuous. If the instance is not running during that hour, the Reserved Instance discount is not applied and those RI hours are lost. Please refer the link below for repost answer to similar RI billing query.

• https://repost.aws/questions/QUy3tcCoUoSKqznBEeG3vieQ/convertible-ri-instances-also-billed-as-on-demand-why#AN4lv3aoZnTyWsQLxIlMksnQ