The answer is to attach the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone. This is correct because web tier high availability across availability zones requires distributing compute resources across physically isolated locations; deploying in only one AZ creates a single point of failure, so adding a second AZ allows traffic to shift to the healthy zone during an outage, achieving resilience with minimal redesign. On the SAA-C03 exam, this scenario tests your understanding of multi-AZ architecture for fault tolerance, often appearing as a trap where candidates mistakenly suggest adding more instances in the same AZ or switching to a different load balancer type. The key insight is that the ALB and ASG must be explicitly associated with subnets in multiple AZs—simply launching more EC2 instances in the same subnet does not solve the problem. Remember the memory tip: “Two subnets, two zones, one resilient throne.”
SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Exhibit
Auto Scaling group: web-asg
Attached subnets: subnet-1111 (us-west-2a)
Load balancer subnets: subnet-1111 (us-west-2a)
Desired capacity: 2
Health check type: ELB
Based on the exhibit, the web tier becomes unavailable if us-west-2a has an outage. What is the best change to improve resilience with the least redesign?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Auto Scaling group: web-asg
Attached subnets: subnet-1111 (us-west-2a)
Load balancer subnets: subnet-1111 (us-west-2a)
Desired capacity: 2
Health check type: ELB
A
Increase the Auto Scaling group desired capacity from 2 to 3 in the same subnet.
Why wrong: Adding more instances in the same Availability Zone does not protect the service from a full AZ outage. The failure domain is still the same.
B
Attach the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone.
Spanning the load balancer and Auto Scaling group across at least two Availability Zones removes the single-AZ dependency shown in the exhibit. If us-west-2a fails, the remaining AZ can continue serving traffic and Auto Scaling can replace unhealthy instances there. This is the smallest architectural change that directly improves availability.
C
Replace the Application Load Balancer with a Network Load Balancer.
Why wrong: A different load balancer type does not fix the fact that all compute and load balancer resources are currently in one Availability Zone. The outage risk remains.
D
Increase the health check grace period so instances stay registered longer.
Why wrong: A longer grace period may reduce premature replacement during startup, but it does not help if the entire Availability Zone fails. The service still has one point of failure.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone.
The web tier is currently deployed in a single Availability Zone (us-west-2a), so an outage of that AZ makes the entire tier unavailable. By attaching the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone, the application can continue serving traffic from the healthy AZ, achieving high availability with minimal architectural changes. This is the standard AWS best practice for multi-AZ resilience.
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 Auto Scaling group desired capacity from 2 to 3 in the same subnet.
Why it's wrong here
Adding more instances in the same Availability Zone does not protect the service from a full AZ outage. The failure domain is still the same.
✓
Attach the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone.
Why this is correct
Spanning the load balancer and Auto Scaling group across at least two Availability Zones removes the single-AZ dependency shown in the exhibit. If us-west-2a fails, the remaining AZ can continue serving traffic and Auto Scaling can replace unhealthy instances there. This is the smallest architectural change that directly improves availability.
Clue confirmation
The clue words "best", "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Replace the Application Load Balancer with a Network Load Balancer.
Why it's wrong here
A different load balancer type does not fix the fact that all compute and load balancer resources are currently in one Availability Zone. The outage risk remains.
✗
Increase the health check grace period so instances stay registered longer.
Why it's wrong here
A longer grace period may reduce premature replacement during startup, but it does not help if the entire Availability Zone fails. The service still has one point of failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think increasing instance count or changing load balancer type improves resilience, but the core issue is the single-AZ deployment, which only multi-AZ subnets can fix.
Detailed technical explanation
How to think about this question
Under the hood, an Application Load Balancer is regional and can route traffic to targets in multiple AZs as long as the subnets are specified. The Auto Scaling group must also launch instances in those subnets; if the group is configured with a single subnet, it will only launch in that AZ. In a real-world scenario, if us-west-2a experiences a power failure, instances in us-west-2b would continue to handle requests, and the ALB would automatically stop routing to the failed AZ's targets based on health checks.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Attach the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone. — The web tier is currently deployed in a single Availability Zone (us-west-2a), so an outage of that AZ makes the entire tier unavailable. By attaching the Application Load Balancer and Auto Scaling group to subnets in a second Availability Zone, the application can continue serving traffic from the healthy AZ, achieving high availability with minimal architectural changes. This is the standard AWS best practice for multi-AZ resilience.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best", "least". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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