Posted On: Apr 29, 2022

Amazon EC2 Auto Scaling Warm Pools now supports configuring your Auto Scaling group to return running instances to a Warm Pool on scale-in. With Warm Pools, you can scale out faster by bringing instances into service from a pre-initialized pool of EC2 instances. Warm Pools are a good fit for applications that have time consuming initialization steps — like loading gigabytes of data, provisioning services, or running custom scripts — that can take several minutes or longer before those EC2 instances are ready to serve traffic. Scale-in to Warm Pool saves you from having to rebuild a new Warm Pool instance during scale-in. Previously, EC2 Auto Scaling would terminate one of the running “in-service” instances during scale-in and then launch and pre-initialize a new instance to replenish the Warm Pool. Now, instances can be placed back into the Warm Pool in the desired state – stopped, or running, but idle.

These features are available through the Amazon SDKs, Amazon Command Line Interface (CLI), and Amazon CloudFormation. Amazon Web Services Management Console support for scale-in to Warm Pools is coming soon. To learn more about this feature, visit the Warm Pool documentation. Scale-in to Warm Pools is available in the Amazon Web Services China (Beijing) Region, operated by Sinnet and the Amazon Web Services China (Ningxia) Region, operated by NWCD.