SAA-C03 Design Resilient Architectures Practice Question
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?
⚠ Common exam trap
Many candidates confuse the ALB health check interval or target type with the Auto Scaling group's lifecycle management, mistakenly thinking that changing how the ALB checks health (interval or target type) will fix the premature replacement, when the correct solution is to adjust the ASG's grace period to align with the application's startup time.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the Auto Scaling group’s health check grace period so it exceeds the ~2-minute initialization time.
The Auto Scaling group's health check grace period allows instances to initialize without being marked unhealthy by the ELB health checks. By setting this grace period to exceed the ~2-minute artifact download time, the ASG will not replace instances that are still starting up, preventing the cascade of terminations and redeployments that caused the outage. This directly addresses the root cause—premature health check failures—without changing the health check configuration or reducing availability once the app is ready.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Increase the Auto Scaling group’s health check grace period so it exceeds the ~2-minute initialization time.
Why this is correct
A health check grace period prevents the Auto Scaling group from treating early health check failures as instance health problems. This avoids terminating instances before the application finishes initializing, which stops the restart/replace loop during deployments while still allowing normal health checks to apply once the app is ready.
- ✗
Add more subnets across additional Availability Zones to distribute the same instances more widely.
Why it's wrong here
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.
Why it's wrong here
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.
Why it's wrong here
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.