The answer is to use an Auto Scaling group with a minimum of two instances across two Availability Zones. This configuration directly improves EC2 availability and fault tolerance by distributing the application across isolated data centers, so if one Availability Zone fails, the Auto Scaling group automatically launches a replacement instance in the remaining healthy zone, and traffic is rerouted via Elastic Load Balancing. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding that fault tolerance requires architectural redundancy at the AZ level, not just at the instance or storage layer—a common trap is mistaking larger instance sizes or multiple subnets within a single AZ for high availability. Remember the key principle: availability is a function of distribution, not size; always spread across at least two AZs. Memory tip: “Two AZs, not two sizes.”
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. 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 company runs a web application on a single EC2 instance. They want to improve availability and fault tolerance with minimal architectural changes. What should they do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an Auto Scaling group with a minimum of two instances across two Availability Zones.
Option D is correct because placing instances in an Auto Scaling group across multiple Availability Zones ensures that if one AZ fails, traffic is routed to the other. Option A is wrong because a larger instance does not add fault tolerance. Option B is wrong because multiple subnets in one AZ still share that AZ's risk. Option C is wrong because multiple EBS volumes do not provide instance-level redundancy.
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.
✗
Attach multiple EBS volumes to the instance.
Why it's wrong here
Multiple volumes do not protect against instance or AZ failure.
✓
Use an Auto Scaling group with a minimum of two instances across two Availability Zones.
Why this is correct
Spreading instances across AZs provides high availability and fault tolerance.
Create multiple subnets in the same Availability Zone.
Why it's wrong here
Single Availability Zone is a single point of failure.
✗
Upgrade to a larger instance type.
Why it's wrong here
Larger instance does not provide fault tolerance.
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 SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Use an Auto Scaling group with a minimum of two instances across two Availability Zones. — Option D is correct because placing instances in an Auto Scaling group across multiple Availability Zones ensures that if one AZ fails, traffic is routed to the other. Option A is wrong because a larger instance does not add fault tolerance. Option B is wrong because multiple subnets in one AZ still share that AZ's risk. Option C is wrong because multiple EBS volumes do not provide instance-level redundancy.
What should I do if I get this SAP-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 SAP-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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Question Discussion
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