The correct answer involves launching instances in multiple Availability Zones, distributing subnets across those AZs, and attaching an Application Load Balancer that is enabled for multiple AZs. This combination ensures high availability by allowing the Auto Scaling group to maintain capacity even if an entire AZ fails, as the load balancer can route traffic to healthy instances in the remaining zones. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of fault-tolerant architecture design, a core objective for the SysOps role. A common trap is thinking a single subnet or a single AZ provides redundancy—it does not, because that creates a single point of failure. Instead, remember that Auto Scaling groups must span at least two AZs with corresponding subnets, and the load balancer must be AZ-aware to distribute traffic. Memory tip: think “three A’s” for Availability, Application Load Balancer, and AZs—all three must work together for true high availability.
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 SysOps administrator is responsible for an Auto Scaling group that runs a critical application. The administrator wants to ensure that the application can recover from an AZ failure. Which THREE steps should the administrator take? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place subnets in each Availability Zone used by the Auto Scaling group.
Options A, B, and D are correct. Launching instances in multiple AZs ensures that if one AZ fails, instances in other AZs continue. Distributing subnets across AZs is necessary for that. Using an ALB in multiple AZs distributes traffic. Option C is incorrect because a single subnet in one AZ does not provide AZ-level redundancy. Option E is incorrect because using only one AZ defeats the purpose.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use EC2 instances in a single Availability Zone to reduce latency.
Why it's wrong here
Single AZ is a single point of failure.
✓
Place subnets in each Availability Zone used by the Auto Scaling group.
Why this is correct
Subnets must exist in each AZ for the Auto Scaling group to use.
Use a single subnet in one Availability Zone to simplify network design.
Why it's wrong here
Single AZ does not provide redundancy.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Reliability and Business Continuity — This question tests Reliability and Business Continuity — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Place subnets in each Availability Zone used by the Auto Scaling group. — Options A, B, and D are correct. Launching instances in multiple AZs ensures that if one AZ fails, instances in other AZs continue. Distributing subnets across AZs is necessary for that. Using an ALB in multiple AZs distributes traffic. Option C is incorrect because a single subnet in one AZ does not provide AZ-level redundancy. Option E is incorrect because using only one AZ defeats the purpose.
What should I do if I get this SOA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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