AWS Reserved Capacity Strategy Flexibility - How Savings Plans Cross-Service Coverage Changes Cost Optimization
AWS Savings Plans deliver cross-service discounts spanning EC2, Fargate, and Lambda, revolutionizing reserved capacity strategy. We analyze how to choose between Compute, EC2, and SageMaker Savings Plans, and compare the flexibility gap with Azure RI.
The Evolution of Reserved Capacity - From RI to Savings Plans
AWS's reserved capacity strategy has evolved significantly since the introduction of Reserved Instances (RI). RI is a discount model tied to specific instance types and regions, offering up to 72% discounts, but it had flexibility challenges when architectures changed. Changing instance types would void the discount, creating a risk of wasted unused RIs. Savings Plans, introduced in 2019, fundamentally solved this problem. The model commits to an hourly spend amount (e.g., $10/hour), and discounts are automatically applied to usage up to the committed amount. It flexibly accommodates changes in instance type, region, OS, and tenancy, and also enables cross-service discounts.
Choosing Between the Three Types of Savings Plans
Savings Plans come in three types: Compute, EC2 Instance, and SageMaker, selected based on the trade-off between flexibility and discount rate. Compute Savings Plans offer the highest flexibility, applying across EC2, Fargate, and Lambda. You can freely change instance family, region, OS, and tenancy, with discount rates up to 66%. EC2 Instance Savings Plans lock in a region and instance family in exchange for deeper discounts of up to 72%. They accommodate instance size and OS changes, so scaling up or down within the same family is not an issue. SageMaker Savings Plans are dedicated to machine learning workloads, applying up to 64% discounts to SageMaker instance usage. In practice, a layered approach of using Compute Savings Plans as a base and supplementing with EC2 Instance Savings Plans for fixed workloads is effective.
The Strategic Value of Cross-Service Coverage
The greatest innovation of Compute Savings Plans is that discounts apply across the computing services EC2, Fargate, and Lambda. This is a design that responds to the evolution of modern cloud architectures. Many enterprises are migrating from EC2-based monolithic architectures to containers (Fargate) and serverless (Lambda), but under the traditional RI model, there was a risk of losing discounts during this migration. With Compute Savings Plans, discounts continue whether you migrate from EC2 to Fargate or refactor from Fargate to Lambda, as long as usage stays within the committed amount. This flexibility is a mechanism that encourages architecture modernization from a pricing perspective, making it possible to align the technically optimal solution with the cost-optimal solution.
Flexibility Comparison with Azure RI
Azure's Reserved Instances offer Instance Size Flexibility, accommodating size changes within the same series. However, they cannot achieve cross-service discounts like AWS Savings Plans. Azure RI must be purchased separately for each service, including VMs, SQL Database, Cosmos DB, and App Service, and purchasing VM RI does not apply to Azure Functions or Azure Container Instances. Azure Hybrid Benefit, which allows bringing Windows Server and SQL Server licenses, is a unique strength but limited to companies that already hold Microsoft licenses. GCP's Committed Use Discounts (CUD) are also limited to compute resources and cannot cross-apply to Cloud Functions or Cloud Run. Cross-service reserved discounts are a model that only AWS Savings Plans has achieved in the industry.
Savings Plans Purchase Strategy and Optimization
When purchasing Savings Plans, leveraging Cost Explorer's recommendation feature is essential. It calculates optimal commitment amounts and estimated savings based on 7-day, 30-day, and 60-day usage patterns. As a purchase strategy, it is recommended to first cover 70-80% of the stable baseline with Compute Savings Plans, then supplement the remaining stable portion with EC2 Instance Savings Plans. Rather than purchasing the full amount at once, a phased approach of incrementally adding coverage while reviewing usage patterns quarterly reduces risk. Payment options include All Upfront, Partial Upfront, and No Upfront, with All Upfront offering the highest discount rate. For those wanting to learn more about reserved capacity strategies, related books on Amazon can also be helpful.
Summary
AWS Savings Plans have revolutionized reserved capacity strategy, establishing the industry's only cross-service discount model. Compute Savings Plans' cross-application across EC2, Fargate, and Lambda is a mechanism that aligns architecture modernization with cost optimization, providing flexibility that Azure RI and GCP CUD cannot match. By layering the three types of Savings Plans and leveraging Cost Explorer's recommendation feature for phased purchases, you can achieve maximum cost savings while minimizing risk.