The correct answer is that the script executed via cfn-signal failed to complete successfully. A CloudFormation WaitCondition fails when it does not receive the required success signal from an EC2 instance or resource within the configured timeout period, and the most common cause is an error in the user data script that runs cfn-signal, such as a syntax error, missing dependency, or a command that exits with a non-zero status. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this question tests your understanding of how CloudFormation handles resource provisioning dependencies and the critical role of cfn-signal in signaling completion. A common trap is to blame network issues or instance size, but the error message explicitly points to a signal failure, not a timeout or connectivity problem. Memory tip: think of cfn-signal as a "handshake" — if the script stumbles, the handshake never happens.
PAS-C01 Technology Practice Question
This PAS-C01 practice question tests your understanding of technology. 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.
Network Topology
Refer to the exhibit. A CloudFormation stack creation failed with the message 'WaitCondition received failed signal'. 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 script executed via cfn-signal failed to complete successfully
Option A is correct because a WaitCondition fails when the expected signal from cfn-signal is not received, often due to a script error. Option B is incorrect because the signal failure is about the script, not instance size. Option C is incorrect because security groups would cause a different error. Option D is incorrect because the error message explicitly mentions a signal failure, not a time limit.
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.
✗
The security group rules are blocking the cfn-signal communication
Why it's wrong here
cfn-signal uses HTTPS to CloudFormation endpoint, not blocked by typical security groups.
✗
The stack creation timed out after 1 hour
Why it's wrong here
Timeout would show a different status reason.
✓
The script executed via cfn-signal failed to complete successfully
Why this is correct
The WaitCondition expects a success signal; failure indicates script error.
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 EC2 instance type is not supported in the region
Why it's wrong here
That would be a different error, not a signal failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Trap categories for this question
Command / output trap
Timeout would show a different status reason.
Detailed technical explanation
How to think about this question
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.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which PAS-C01 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.
Technology — This question tests Technology — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The script executed via cfn-signal failed to complete successfully — Option A is correct because a WaitCondition fails when the expected signal from cfn-signal is not received, often due to a script error. Option B is incorrect because the signal failure is about the script, not instance size. Option C is incorrect because security groups would cause a different error. Option D is incorrect because the error message explicitly mentions a signal failure, not a time limit.
What should I do if I get this PAS-C01 question wrong?
Identify which PAS-C01 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.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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