Question

A DevOps team manages a stateless web tier on an EC2 Auto Scaling group behind an Application Load Balancer. They deploy a new AMI using an instance refresh with a minimum healthy percentage of 90% and a health check grace period of 300 seconds. During the refresh, the new AMI contains a misconfiguration that causes instances to pass EC2 status checks but fail the ALB target group HTTP health check. The team wants the instance refresh to detect these failures and stop replacing instances automatically before the entire fleet is cycled. Which configuration change ensures the instance refresh halts when the new instances are unhealthy?

Accepted Answer

Set the Auto Scaling group health check type to ELB and enable checkpoints so the instance refresh evaluates ELB health during each phase.

Answer

Increase the health check grace period to 900 seconds so the ALB has more time to mark the new instances healthy before continuing.

Answer

Lower the minimum healthy percentage to 50% so more instances are replaced simultaneously and failures surface faster.

Answer

Attach a scheduled scaling action that scales in the group if CloudWatch UnHealthyHostCount exceeds zero during the deployment window.