An engineering team deploys a stateless web API on EC2 using an Auto Scaling group and an Application Load Balancer (ALB). During a recent test, they noticed that when one Availability Zone was unavailable, traffic failed until new instances were manually launched. Which change most directly improves automatic failover for the compute layer within a single Region?

Place the Auto Scaling group in only one subnet so instance launches are simpler.

Using only one subnet/AZ removes redundancy. An AZ outage would still take down capacity until manual action occurs.

Increase the target group deregistration delay to allow old instances to stay longer.

Changing deregistration delay affects connection draining, not capacity placement across AZs. It doesn’t create additional resilient instances.

Use a Network Load Balancer, but keep all subnets in a single Availability Zone.

Switching load balancer type doesn’t fix the root cause. If capacity is only in one AZ, failures will still impact the service.

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: Ensure the ALB and Auto Scaling group span multiple subnets in at least two Availability Zones. — To achieve automatic failover for stateless compute within a Region, the ALB and the Auto Scaling group must provide capacity in more than one Availability Zone. When both are associated with subnets across at least two AZs, the ALB can continue routing requests to healthy targets in surviving AZs. This design reduces manual intervention during AZ impairment and improves overall availability for the compute tier. Why others are wrong: Restricting the Auto Scaling group to one subnet/AZ eliminates redundancy, so an AZ outage still breaks service. Deregistration delay tweaks do not increase resiliency; they only influence how connections are handled during instance lifecycle events. Using a different load balancer while keeping single-AZ placement still leaves the same single point of failure.

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.