In cloud computing, elasticity is a term used to reference the ability of a system to adapt to changing workload demand by provisioning and deprovisioning pooled resources so that provisioned resources match current demand as well as possible.
Suggested Reads:
Reserved Instance Planner: Why, When and How to use your RIs?
Why Cost Management for your Cloud is Beyond Essential?
AWS Performance Optimization Checks
Rightsizing: The Secret Key to Unlock Cloud Cost Optimization