A web application runs on an Amazon EC2 Auto Scaling group behind an Application Load Balancer (ALB). After each deployment, new instances take about 2 minutes to download artifacts and become ready to accept requests on the target port. In the last deployment, the ALB started marking targets unhealthy before the app was ready, and the Auto Scaling group then replaced those instances repeatedly, causing a prolonged outage. Which change best improves resilience during instance start-up without reducing actual availability once the application is healthy?

Add more subnets across additional Availability Zones to distribute the same instances more widely.

Adding subnets/AZs increases fault tolerance, but it does not address the immediate cause of the outage: the target group (via ALB health checks) is marking instances unhealthy before the application is ready. The unhealthy/replace loop would still occur for each instance that starts during deployments.

Switch the load balancer target type from instance targets to IP targets to avoid health check failures.

Target type does not change application readiness. Even with IP targets, the ALB health check fails until the application starts responding on the configured health check path/port, so the Auto Scaling group would still see unhealthy targets and replace instances.

Reduce the ALB health check interval so unhealthy targets are removed faster.

Reducing the interval makes ALB detect failure conditions sooner. With a ~2-minute initialization time, this increases the chance that instances are marked unhealthy and replaced before they can become ready, making the problem worse rather than improving start-up resilience.

What does this SAA-C03 question test?

CIDR notation defines the prefix length.

What is the correct answer to this question?

The correct answer is: Increase the Auto Scaling group’s health check grace period so it exceeds the ~2-minute initialization time. — When an Auto Scaling group is attached to an ALB target group, health checks can drive instance replacement. If the application needs ~2 minutes to become ready, the ALB will mark targets unhealthy during that window unless you allow time for initialization. Setting an appropriate Auto Scaling health check grace period ensures those initial health check failures are not treated as grounds to terminate/replace the instance. After the grace period, normal health checks apply, so availability once the app is healthy is not reduced—resilience during deployments is improved by avoiding a premature termination loop. Adding AZs improves infrastructure fault tolerance but does not fix the startup timing mismatch that causes ALB to mark targets unhealthy and trigger Auto Scaling churn. Changing target type does not affect whether the application responds to ALB health checks. Reducing the health check interval increases the likelihood of premature unhealthy status during deployments, worsening churn.

What should I do if I get this SAA-C03 question wrong?

Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.