- A
Increase the ASG desired capacity so that extra instances absorb the failed ones.
Why wrong: This adds capacity, but it does not make the group react to application-level failure faster or more accurately.
- B
Set the Auto Scaling group health check type to ELB so target group health determines replacement.
This makes Auto Scaling replace instances that fail the load balancer health check even when EC2 status checks still pass. The exhibit shows the application health endpoint returns 500 while EC2 checks remain passing, so EC2-only health checks miss the failure. ELB-based health checks align replacement with real application availability.
- C
Replace the Application Load Balancer with a Network Load Balancer to improve failover speed.
Why wrong: A Network Load Balancer changes the traffic layer, but it does not solve the instance-replacement problem shown in the exhibit.
- D
Increase the HealthCheckGracePeriod to the maximum value so the instances have more time to stabilize.
Why wrong: A longer grace period delays health evaluation after launch, but the unhealthy instances here are already running and returning 500 responses.
Quick Answer
The answer is to set the Auto Scaling group health check type to ELB so that target group health determines replacement. This is correct because the default EC2 health check only verifies that an instance is in a running state, not whether the application process inside it is actually responding. By switching to an ELB health check, the Auto Scaling group uses the target group’s application-level probes—such as HTTP 200 responses—so when the application fails, the ELB marks the instance unhealthy and the ASG immediately terminates and replaces it. On the SAA-C03 exam, this scenario tests your understanding of the difference between infrastructure-level and application-level health monitoring; a common trap is assuming EC2 status checks alone cover application recovery. Remember the memory tip: “EC2 checks the machine, ELB checks the app.”
SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Based on the exhibit, the application tier is not replacing unhealthy instances even though the Auto Scaling group spans two Availability Zones. What change most directly improves automatic recovery when the application process fails?
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
Set the Auto Scaling group health check type to ELB so target group health determines replacement.
Option B is correct because setting the Auto Scaling group health check type to ELB allows the ASG to use the target group's health checks, which monitor application-level health (e.g., HTTP 200 responses). When the application process fails, the ELB marks the instance as unhealthy, and the ASG immediately terminates and replaces it. This directly addresses the issue of unhealthy instances not being replaced, as the default EC2 health check only verifies instance status (e.g., running vs. stopped), not application responsiveness.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 ASG desired capacity so that extra instances absorb the failed ones.
Why it's wrong here
This adds capacity, but it does not make the group react to application-level failure faster or more accurately.
- ✓
Set the Auto Scaling group health check type to ELB so target group health determines replacement.
Why this is correct
This makes Auto Scaling replace instances that fail the load balancer health check even when EC2 status checks still pass. The exhibit shows the application health endpoint returns 500 while EC2 checks remain passing, so EC2-only health checks miss the failure. ELB-based health checks align replacement with real application availability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Replace the Application Load Balancer with a Network Load Balancer to improve failover speed.
Why it's wrong here
A Network Load Balancer changes the traffic layer, but it does not solve the instance-replacement problem shown in the exhibit.
- ✗
Increase the HealthCheckGracePeriod to the maximum value so the instances have more time to stabilize.
Why it's wrong here
A longer grace period delays health evaluation after launch, but the unhealthy instances here are already running and returning 500 responses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the default EC2 health check is sufficient for application-level failures, but it only checks instance state (running/stopped), not the application process, so the ASG never triggers replacement for application crashes.
Trap categories for this question
Command / output trap
A Network Load Balancer changes the traffic layer, but it does not solve the instance-replacement problem shown in the exhibit.
Detailed technical explanation
How to think about this question
The default EC2 health check for an Auto Scaling group only checks the instance's system status (e.g., reachability via EC2 status checks), not the application running inside it. By switching to ELB health checks, the ASG relies on the target group's health checks, which can be configured to probe a specific path (e.g., /health) at Layer 7, ensuring that only instances with a healthy application process are kept. This is critical in multi-AZ deployments where an instance may be running but its application is unresponsive, as the ELB health check will detect the failure and trigger replacement via the ASG lifecycle hooks.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Resilient Architectures — This question tests Design Resilient Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set the Auto Scaling group health check type to ELB so target group health determines replacement. — Option B is correct because setting the Auto Scaling group health check type to ELB allows the ASG to use the target group's health checks, which monitor application-level health (e.g., HTTP 200 responses). When the application process fails, the ELB marks the instance as unhealthy, and the ASG immediately terminates and replaces it. This directly addresses the issue of unhealthy instances not being replaced, as the default EC2 health check only verifies instance status (e.g., running vs. stopped), not application responsiveness.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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