The answer is that the engine version upgrade is not supported for Multi-AZ deployments, which causes the CloudFormation update to fail and roll back. This occurs because modifying the DB engine version on a Multi-AZ RDS instance requires a coordinated reboot of both the primary and standby replicas, and if the target version is incompatible with the Multi-AZ configuration—such as when the upgrade path is blocked or the new engine version does not support Multi-AZ—the operation cannot proceed. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of RDS lifecycle operations within CloudFormation, specifically how Multi-AZ constraints interact with in-place modifications. A common trap is assuming any engine version change is allowed, but AWS enforces supported upgrade paths for Multi-AZ instances. Remember the mnemonic: “Multi-AZ upgrade? Check the path—if it’s blocked, the stack gets sacked.”
SOA-C02 Deployment, Provisioning, and Automation Practice Question
This SOA-C02 practice question tests your understanding of deployment, provisioning, and automation. 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 uses AWS CloudFormation to deploy a stack that includes an Amazon RDS DB instance with Multi-AZ enabled. During a stack update, the database engine version is changed. The update fails with a rollback. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The engine version upgrade is not supported for Multi-AZ deployments.
Option C is correct because modifying the DB engine version on a Multi-AZ instance requires a reboot of both the primary and standby, and if the upgrade is not supported, it fails. Option A is wrong because the storage type is not changed. Option B is wrong because the DB instance class is not changed. Option D is wrong because the subnet group is not changed.
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.
✓
The engine version upgrade is not supported for Multi-AZ deployments.
Why this is correct
Some engine version upgrades are not supported directly; they may require a manual process.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The DB instance class is not available for the new engine version.
Why it's wrong here
The instance class is not changed.
✗
The storage type is not compatible with the new engine version.
Why it's wrong here
The storage type is not mentioned; engine version changes typically don't affect storage type compatibility.
✗
The DB subnet group does not have enough IP addresses.
Why it's wrong here
Subnet group IP addresses are not related to engine version upgrades.
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
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.
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.
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The engine version upgrade is not supported for Multi-AZ deployments. — Option C is correct because modifying the DB engine version on a Multi-AZ instance requires a reboot of both the primary and standby, and if the upgrade is not supported, it fails. Option A is wrong because the storage type is not changed. Option B is wrong because the DB instance class is not changed. Option D is wrong because the subnet group is not changed.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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