Start simple: idle resources, non-critical development/QA and previous generation instances will require less testing hours and provide quick wins (The Amazon EC2 Launch time statistics can be used to identify instances that have been running longer than others and is a good statistic to sort your Amazon EC2 instances by).
Right Size before performing a migration: If you skip right sizing to save time, your migration speed might increase, but you will end up with higher cloud infrastructure spend for a potentially longer period of time. Instead, leverage the test and QA cycles during a migration exercise to test several instance types and families. Also, take that opportunity to test different sizes and burstable instances like the “t” family.
The best right sizing starts on day 1: As you perform right sizing analysis, and ultimately rightsize resources, ensure any learnings are being shared across your organization and influencing the design of new workloads and upcoming migrations.
Measure Twice, Cut Once: Test, then test some more: The last thing you want is for a new resource type to be uncapable of handling load, or functioning incorrectly.
Test once and perform multiple right sizing: Aggregate instances per autoscaling group and tags to scale right sizing activities.
Combine Reserved Instance or Savings Plans strategy with Right Sizing to maximize savings: For Standard RIs and EC2 Instance SP: Perform your pricing model purchases after rightsizing and for Convertible RIs, exchange them after rightsizing. Compute Savings plan will automatically adjust the commitment for the new environment.
Ignore burstable instance families (T types): These families are designed to typically run at low CPU percentages for significant periods of time and shouldn’t be part of the instance types being analyzed for rightsizing.