How to commit part of instances to Saving Plan

Yes, you can choose to purchase Savings Plan for a part of your usage. Savings Plan work on hourly commitments (measured in $/hour) so when you purchase a Savings Plan you will be asked for the following: Savings Plan Type - Could be Compute/ EC2/ SageMaker; Term - 1 year/ 3 years; Purchase Commitment - Here you need to enter the hourly commitment in USD; Payment Option - All Upfront/ Partial Upfront/ No Upfront.

If you go for EC2 Savings Plan, you will be asked for the Region and Instance Family details as well. This is because EC2 Instance Savings Plans give you the flexibility to change your usage between instances within a family in that region.

To understand what could be a baseline for your hourly commitment, you can view the Savings Plans recommendations provided in AWS Cost Explorer. The recommended hourly commitment is based on your historical On Demand usage and your choice of plan type, term length, and payment option. Once you sign up for a Savings Plan, your compute usage will automatically be charged at the discounted Savings Plans prices and any usage beyond your commitment will be charged at regular On Demand rates.

In this case, as you have T3 and M5 instance families, you can go for one Compute Savings Plan or two EC2 Savings Plan depending on your requirements. Compute Savings Plan would provide you with the most flexibility while EC2 Savings Plan would provide the lowest prices.