A web application runs on an Amazon EC2 Auto Scaling group (ASG) behind an Application Load Balancer (ALB). The ALB is configured to use at least two Availability Zones (AZs), but the ASG currently uses subnets in only one AZ. If that AZ becomes unavailable, the application stops serving requests. Which change most directly improves resilience to an AZ outage?

Keep the ASG in one Availability Zone, but reduce ALB health check intervals.

Reducing health check intervals only changes how quickly the ALB marks targets unhealthy. It does not create capacity in other AZs, so the ALB still has no healthy instances to route to when the only ASG AZ fails.

Switch the load balancer from an ALB to an NLB to remove HTTP health check dependency.

Changing from ALB to NLB does not address the root cause: there is no instance capacity in other AZs. Without multi-AZ compute capacity, any load balancer cannot serve traffic during the AZ outage.

Add an Amazon SQS queue to buffer requests during failures.

A queue can help with asynchronous work, but a typical web request/response path still requires immediate compute capacity to accept and handle requests. Queueing does not eliminate the loss of in-AZ instances when the only ASG AZ fails.

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: Place the ASG across multiple Availability Zones by configuring it with subnets in at least two AZs. — To continue serving traffic during an Availability Zone outage, the system must have running compute capacity in more than one AZ. Because the ASG determines where instances can run (based on the subnets/AZs configured for the ASG), configuring the ASG to use subnets in at least two AZs directly addresses the failure domain. With multi-AZ targets available, the ALB can route to healthy instances in the surviving AZ and the ASG can replace any instances that fail during the outage. Option A only accelerates detection/marking of unhealthy targets; it does not add targets in other AZs. Option C changes load balancer type, but does not create multi-AZ compute. Option D introduces buffering, which may help with asynchronous workflows, but it does not ensure the application can accept and process synchronous web traffic when one AZ containing the only ASG capacity becomes unavailable.

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.