Quick Answer
The answer is that the EC2 instance resource configuration has an error. This is the most likely cause because CloudFormation creates resources in parallel where possible, but when a resource fails to launch—often due to a misconfiguration like an invalid AMI ID, incorrect instance type, or a missing parameter—it triggers a “Resource creation cancelled” error for any remaining dependent resources. In this scenario, the security group succeeded, but the instance failed, so CloudFormation cancels the creation of subsequent resources and begins a rollback. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of CloudFormation’s parallel creation behavior and dependency handling; a common trap is assuming the error means the security group failed or that a manual rollback trigger is required. Remember: if one resource fails, CloudFormation cancels the rest—think of it as a “chain reaction” where a single broken link stops the whole stack.
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 manage infrastructure. They have a stack that creates an Amazon EC2 instance and an associated security group. The stack creation fails with the error: 'Resource creation cancelled' after the security group is created but before the instance is launched. 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.
The security group failed to create.
Why wrong: The security group was created successfully.
The stack was manually deleted during creation.
Why wrong: No evidence of manual deletion.
The EC2 instance resource configuration has an error.
The instance likely has a misconfiguration causing creation cancellation.
The stack's rollback trigger was not configured.
Why wrong: Rollback trigger is not required for failed creation.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The EC2 instance resource configuration has an error.
Option D is correct because CloudFormation typically creates resources in parallel, but if one resource fails, it cancels others. The error indicates a dependency issue or a misconfiguration in the instance resource. Option A is wrong because the security group was created successfully. Option B is wrong because the stack was not deleted. Option C is wrong because AWS CloudFormation does not require a rollback trigger for a failed resource creation; it automatically rolls back.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The security group failed to create.
Why it's wrong here
The security group was created successfully.
The stack was manually deleted during creation.
Why it's wrong here
No evidence of manual deletion.
The EC2 instance resource configuration has an error.
Why this is correct
The instance likely has a misconfiguration causing creation cancellation.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
The stack's rollback trigger was not configured.
Why it's wrong here
Rollback trigger is not required for failed creation.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Identify which SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: The EC2 instance resource configuration has an error. — Option D is correct because CloudFormation typically creates resources in parallel, but if one resource fails, it cancels others. The error indicates a dependency issue or a misconfiguration in the instance resource. Option A is wrong because the security group was created successfully. Option B is wrong because the stack was not deleted. Option C is wrong because AWS CloudFormation does not require a rollback trigger for a failed resource creation; it automatically rolls back.
Identify which SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
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