Pricing Of EC2 Instances: Saving Plan and Reserved Instances

Hello,

When choosing a Convertible Reserved Instance on AWS, it means that if you need to change the instance type, size, or other attributes, you must manually initiate an exchange to update your reservation, unlike a Savings Plan which automatically applies cost savings based on your current usage across different instance types without requiring manual intervention; essentially, with a convertible reserved instance, you have the flexibility to adjust your reservation, but you need to actively make the changes yourself, while a Savings Plan adapts to your needs automatically.

Should you have any additional questions, you're welcome to reach out to our Sales/Business Development team here: https://aws.amazon.com/contact-us/sales-support/.

— Andy M.

Your understanding of EC2 pricing options is generally on the right track, but there are some details that need clarification:

Compute Savings Plans: You're correct that these offer the most flexibility. You commit to a specific dollar amount per hour for either 1 or 3 years. This applies across EC2 instances, AWS Fargate, and AWS Lambda, regardless of instance family, size, region, OS, or tenancy. You can change instance types or even services as needed without modifying your plan. To "upgrade," you would indeed need to increase your hourly commitment.

EC2 Instance Savings Plans: Your understanding here is mostly correct, but with a few adjustments. You commit to a specific EC2 instance family in a chosen region. While you don't specify the exact size, you do commit to a dollar amount per hour. You have flexibility in instance size, OS, and tenancy within that family and region. However, you cannot change the region or instance family without getting a new plan.

Standard Reserved Instances: Your description is accurate. These are the least flexible, requiring commitments to a specific instance family, size, OS, tenancy, and region. They cannot be changed without exchanging or modifying the reservation.

Convertible Reserved Instances: You've described these as "Reserved Flexible," which is close. They do offer more flexibility than Standard RIs, allowing changes in instance family, size, OS, tenancy, and region. However, these changes require manual exchanges, unlike the automatic application of Savings Plans.

All of these options offer discounts compared to On-Demand pricing, with potential savings ranging from up to 66% for Compute Savings Plans to up to 72% for EC2 Instance Savings Plans and Standard RIs. The choice between them depends on your specific needs for flexibility versus maximum savings.
Sources
Savings Plans - Amazon EC2 Reserved Instances and Other AWS Reservation Models
Compute Savings Plans and Reserved Instances - Savings Plans
Main Differences b/t EC2 Saving Plans (Compute and Instance) and Reserved Instances | AWS re:Post