Question

A company runs a stateless web application on an EC2 Auto Scaling group spanning three Availability Zones behind an Application Load Balancer. After a large scale-in event followed by manual instance terminations during troubleshooting, a SysOps administrator notices that 8 of the 10 running instances are concentrated in a single Availability Zone. The team is concerned that an AZ failure could remove most of the fleet's capacity. Which action will BEST ensure the Auto Scaling group maintains a balanced distribution of instances across the Availability Zones going forward?

Accepted Answer

Rely on the Auto Scaling group's default AZ rebalancing, which automatically launches instances in under-provisioned AZs and terminates instances in over-provisioned AZs to restore balance.

Answer

Configure a target tracking scaling policy based on average CPU utilization so that new instances are spread evenly across AZs during scale-out.

Answer

Manually terminate the extra instances in the crowded AZ and launch replacements in the other AZs each time an imbalance is detected.

Answer

Enable cross-zone load balancing on the Application Load Balancer so traffic is distributed evenly regardless of instance placement per AZ.