A mission-critical application runs continuously and uses EC2, Fargate, and Lambda across multiple Regions and operating systems. The company wants maximum cost savings while keeping the flexibility to change workloads. Which purchasing option best meets these goals?

A Compute Savings Plan offers the most flexibility and cost savings for this scenario. It applies to EC2, Fargate, and Lambda usage, regardless of instance family, Region, or operating system, as long as the usage is within the committed spend. This allows for workload changes while still benefiting from discounted rates. An EC2 Instance Savings Plan is too restrictive as it only covers EC2 instances and requires commitment to a specific instance family in a Region. Reserved Instances are even more rigid, requiring commitments to specific instance types, OS, Region, and tenancy, which doesn't align with the need for flexibility. EC2 Spot Instances offer significant savings but are not suitable for mission-critical, continuously running applications due to their interruptible nature.