AWS Certified Solutions Architect Professional SAP-C02 Practice Question

Enabling Capacity Rebalancing causes EC2 Auto Scaling to monitor for the EC2 instance rebalance recommendation that Spot Instances receive when they are at elevated risk of interruption. When the signal is detected, Auto Scaling launches a replacement Spot Instance and waits for it to pass health checks before terminating the at-risk instance. To ensure this process is not blocked by capacity limits, Auto Scaling can temporarily exceed the group's maximum size by a margin (by default, 10% of the desired capacity). This proactive replacement keeps the group at or above its desired capacity and requires only a single setting change.

A lifecycle hook for the EC2_INSTANCE_TERMINATING state is reactive, as it triggers when the instance is already being terminated, not when the earlier rebalance recommendation is issued. Raising the minimum capacity adds fixed cost and does not guarantee proactive replacement. Predictive scaling launches capacity based on historical demand patterns; it does not respond to real-time Spot rebalance events and therefore cannot guarantee capacity during unexpected interruptions.