Amazon EC2 introduces a new capability that makes it easy for customers to target instance launches on their On-Demand Capacity Reservations (ODCRs). On-Demand Capacity Reservations help you reserve compute capacity for your workloads in a specific Availability Zone for any duration. This new feature allows you to better utilize your On-Demand Capacity Reservations by ensuring that launches from the RunInstances EC2 API and EC2 Auto Scaling groups will only be fulfilled by your targeted or open Capacity Reservations.
To get started, customers simply specify they if want to only launch on ODCR capacity on either their RunInstances EC2 API, Launch Templates, or Auto-Scaling Groups (ASGs).
This capability is now available in all AWS Regions, except China regions. To get started, please refer to the documentation for use with RunInstances API and ASG.
Source:: Amazon AWS