SOA-C02 Reliability and Business Continuity Practice Question
This SOA-C02 practice question tests your understanding of reliability and business continuity. 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 web application runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. To achieve high availability, what is the minimum number of Availability Zones (AZs) that must be configured for the Auto Scaling group?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
2
For high availability, an Auto Scaling group must span at least two Availability Zones (AZs) to ensure that if one AZ fails, the application remains available from the other AZ. A single AZ would create a single point of failure, violating the high-availability requirement. The Application Load Balancer distributes traffic across healthy instances in all configured AZs, so two AZs are the minimum to achieve fault tolerance.
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.
✗
1
Why it's wrong here
Incorrect. A single AZ does not provide high availability; a failure in that AZ would cause downtime.
✓
2
Why this is correct
Correct. Two AZs are sufficient to maintain availability during an AZ failure, meeting the basic requirement for high availability.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
3
Why it's wrong here
Incorrect. Three AZs provide even better resilience but are not the minimum required for high availability.
✗
4
Why it's wrong here
Incorrect. Four AZs exceed the minimum requirement and are used for additional fault tolerance, not as a baseline.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think a single AZ is sufficient if the Auto Scaling group can replace failed instances, but they overlook that the AZ itself is a failure domain, and high availability requires redundancy across at least two AZs.
Detailed technical explanation
How to think about this question
Under the hood, the Auto Scaling group launches instances across the specified AZs, and the Application Load Balancer uses cross-zone load balancing by default to distribute traffic evenly. In a real-world scenario, if an AZ experiences a complete outage, the Auto Scaling group automatically launches replacement instances in the remaining healthy AZs, and the ALB stops routing traffic to the failed AZ, ensuring continuous availability. The minimum of two AZs is a common architectural best practice codified in the AWS Well-Architected Framework for fault tolerance.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Reliability and Business Continuity — This question tests Reliability and Business Continuity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 2 — For high availability, an Auto Scaling group must span at least two Availability Zones (AZs) to ensure that if one AZ fails, the application remains available from the other AZ. A single AZ would create a single point of failure, violating the high-availability requirement. The Application Load Balancer distributes traffic across healthy instances in all configured AZs, so two AZs are the minimum to achieve fault tolerance.
What should I do if I get this SOA-C02 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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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