- A
Place the instances in a single subnet and increase the instance size.
Why wrong: This does not add automatic recovery or remove unhealthy instances from service.
- B
Use an Application Load Balancer with an Auto Scaling group and configure health checks.
An Application Load Balancer distributes traffic across healthy targets, and an Auto Scaling group can replace instances that fail health checks. Together, they provide automatic recovery from instance failure and keep the application available across multiple Availability Zones. This is the standard resilient design for stateless EC2 web tiers.
- C
Use a network ACL to detect failed instances and restart them.
Why wrong: Network ACLs filter traffic, but they do not monitor instance health or restart servers.
- D
Store the web servers on EBS volumes so the data survives failures.
Why wrong: Persistent storage alone does not automatically recover failed compute instances or shift traffic.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure 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.
A stateless web application runs on Amazon EC2 instances across two Availability Zones. The team wants unhealthy instances to be removed automatically and replaced without manual action. What is the best solution?
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.
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
Use an Application Load Balancer with an Auto Scaling group and configure health checks.
Option B is correct because an Application Load Balancer (ALB) with an Auto Scaling group provides automated health checks and instance replacement. The ALB performs HTTP/HTTPS health checks against the instances, and when an instance fails the health check, the Auto Scaling group automatically terminates the unhealthy instance and launches a new one to maintain the desired capacity. This ensures the stateless web application remains available across both Availability Zones without manual intervention.
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.
- ✗
Place the instances in a single subnet and increase the instance size.
Why it's wrong here
This does not add automatic recovery or remove unhealthy instances from service.
When this WOULD be correct
This option would be correct if the question asked for a solution to handle increased load for a single-instance application that does not require high availability, and the goal was to vertically scale the instance to improve performance.
- ✓
Use an Application Load Balancer with an Auto Scaling group and configure health checks.
Why this is correct
An Application Load Balancer distributes traffic across healthy targets, and an Auto Scaling group can replace instances that fail health checks. Together, they provide automatic recovery from instance failure and keep the application available across multiple Availability Zones. This is the standard resilient design for stateless EC2 web tiers.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a network ACL to detect failed instances and restart them.
Why it's wrong here
Network ACLs filter traffic, but they do not monitor instance health or restart servers.
When this WOULD be correct
A question asks for a security layer to block specific IP ranges from accessing a subnet, or to allow/deny traffic at the subnet boundary based on source/destination IP and port. In that context, a network ACL is the correct answer.
- ✗
Store the web servers on EBS volumes so the data survives failures.
Why it's wrong here
Persistent storage alone does not automatically recover failed compute instances or shift traffic.
When this WOULD be correct
If the question required ensuring data persistence for stateful applications after instance failure, such as a database server where data must survive termination, then using EBS volumes with termination protection would be correct.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Use an Application Load Balancer with an Auto Scaling group and configure health checks.Correct answer▾
Why this is correct
An Application Load Balancer distributes traffic across healthy targets, and an Auto Scaling group can replace instances that fail health checks. Together, they provide automatic recovery from instance failure and keep the application available across multiple Availability Zones. This is the standard resilient design for stateless EC2 web tiers.
✗Place the instances in a single subnet and increase the instance size.Wrong answer — click to see why▾
Why this is wrong here
Placing instances in a single subnet and increasing instance size does not provide automatic unhealthy instance replacement; it only increases capacity within one Availability Zone, offering no fault tolerance or self-healing.
★ When this WOULD be the correct answer
This option would be correct if the question asked for a solution to handle increased load for a single-instance application that does not require high availability, and the goal was to vertically scale the instance to improve performance.
Why candidates choose this
Candidates may think that a larger instance can handle failures better, or they confuse vertical scaling with the automatic recovery provided by Auto Scaling groups.
✗Use a network ACL to detect failed instances and restart them.Wrong answer — click to see why▾
Why this is wrong here
Network ACLs are stateless packet filters at the subnet level; they cannot detect failed instances or trigger instance replacement. They do not perform health checks or automate recovery.
★ When this WOULD be the correct answer
A question asks for a security layer to block specific IP ranges from accessing a subnet, or to allow/deny traffic at the subnet boundary based on source/destination IP and port. In that context, a network ACL is the correct answer.
Why candidates choose this
Candidates may confuse network ACLs (which filter traffic) with health check mechanisms, or mistakenly think ACLs can monitor instance health and trigger actions.
✗Store the web servers on EBS volumes so the data survives failures.Wrong answer — click to see why▾
Why this is wrong here
Storing web servers on EBS volumes does not automate instance replacement or health checks; it only preserves data across failures, but manual action is still required to replace failed instances.
★ When this WOULD be the correct answer
If the question required ensuring data persistence for stateful applications after instance failure, such as a database server where data must survive termination, then using EBS volumes with termination protection would be correct.
Why candidates choose this
Candidates may think that preserving data on EBS volumes automatically handles failures, confusing data durability with instance recovery automation.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse network ACLs (stateless packet filters) with health check mechanisms, or assume that persistent storage (EBS) alone provides high availability without an orchestration layer like Auto Scaling.
Detailed technical explanation
How to think about this question
Under the hood, the ALB health check pings the configured endpoint (e.g., /health) at a specified interval (default 30 seconds) with a configurable threshold (e.g., 2 consecutive failures marks unhealthy). The Auto Scaling group uses Amazon EC2 Auto Scaling lifecycle hooks and the EC2 instance status checks to coordinate termination and launch, ensuring the replacement instance is registered with the ALB only after passing its initial health check. In a real-world scenario, if the health check path is misconfigured (e.g., returns a 404), the ALB will mark all instances as unhealthy, triggering a full replacement cycle that could cause an outage.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an Application Load Balancer with an Auto Scaling group and configure health checks. — Option B is correct because an Application Load Balancer (ALB) with an Auto Scaling group provides automated health checks and instance replacement. The ALB performs HTTP/HTTPS health checks against the instances, and when an instance fails the health check, the Auto Scaling group automatically terminates the unhealthy instance and launches a new one to maintain the desired capacity. This ensures the stateless web application remains available across both Availability Zones without manual intervention.
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". 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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Last reviewed: Jun 11, 2026
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