An application on EC2 instances in an Auto Scaling group must download and process growing S3 data during startup, causing multi-minute delays for new instances. What is the MOST cost-effective way to reduce the time before new instances are ready to serve requests?

The correct option is the most cost-effective because a warm pool with instances in the Stopped state incurs charges only for storage, not for compute, significantly reducing costs compared to Running instances. When new capacity is needed, these pre-configured instances start much faster than launching new ones from an AMI, as the S3 data processing is already complete. The autoscaling:EC2INSTANCELAUNCHING lifecycle hook ensures that the instance is not put into service until the application signals it's fully ready, preventing traffic from being routed to an uninitialized instance. Increasing the maximum instance count alone does not address the startup delay or cost-effectiveness. Using Running instances in a warm pool would reduce startup time but would be more expensive due to continuous compute charges. Placing an instance in Standby after it's ready doesn't solve the initial startup delay or cost issue and is not the primary purpose of the Standby state in this context.