EC2 Spot Instances vs. AWS Savings Plans: What are the Potential Savings?

Some of our customers have been asking what the potential savings benefits are for using EC2 Spot Instances over AWS Savings Plans, so I wanted to take some time to address that here. 

EC2 Spot instances are discounted up to 90%, depending on which EC2 instance type, AWS region, and Availability Zone you select. On average, you’ll find savings between 50 and 70%. Spot instances are billed on a per-second basis, with a minimum of one minute. Keep in mind that per-second billing applies to EC2 instances running free editions of Linux, such as Amazon Linux 2, CentOS, or Ubuntu. If you’re running EC2 Spot Instances with a Microsoft Windows operating system, you are billed on an hourly basis, but still benefit from deep discounts on the hourly rate.

The caveat to EC2 Spot Instances is that AWS can reclaim the capacity with a two-minute warning. If you have workloads that aren’t critical, or only need to scale up on a temporary basis, EC2 Spot Instances are an excellent option. 

In contrast, AWS Savings Plans share many similarities with Reserved Instances, or just “RIs.” Like RIs, Savings Plans require that you commit to a 1-year or 3-year period. AWS Savings Plans are an excellent choice if you plan to utilize a baseline amount of compute performance over a longer period of time. While AWS Savings Plans offer up to 72% savings on your AWS compute costs, the average range of savings is between 20 and 50%. 

There are two types of savings plans available: EC2 Instance and Compute. While the EC2 Instance Savings Plans provide slightly higher discounts, Compute Savings Plans give you the most flexibility with compute consumption, including EC2, Fargate, and Lambda (serverless).

Given these two options, which should you choose? I would recommend leaning towards EC2 Spot Instances whenever possible, as there is no time commitment, and the discounts are significant. If your application is not able to handle unexpected downtime, stores state locally, or is otherwise mission critical, then you should lean towards AWS Savings Plans.