The correct answer is a circular dependency between the Lambda function and the custom resource that depends on it. When a CloudFormation template defines both a Lambda function and a custom resource that invokes that same function, CloudFormation cannot determine which resource to create first—the function must exist before the custom resource can call it, but the custom resource may be needed to create dependencies for the function. This creates a deadlock where the function is never deployed, resulting in the "Function not found" error despite the ARN being correct and the function existing in the account. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of CloudFormation resource dependency resolution and the common pitfall of circular references in custom resource patterns. A frequent trap is assuming the error is due to IAM permissions or a malformed ARN, but the real issue is deployment ordering. Remember the memory tip: "If the function isn't found but exists, check the template's dependency chain—circular logic is the pain."
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc 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.
Refer to the exhibit. An AWS CloudFormation template includes a Lambda function with the ARN shown. The function is part of a custom resource to create an S3 bucket. The stack creation fails with the error 'Function not found: arn:aws:lambda:us-east-1:123456789012:function:my-function'. The Lambda function exists in the same account and region. 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 Lambda function is defined in the same template and has a circular dependency
The error indicates that CloudFormation cannot find the Lambda function. Since the function exists in the same account and region, the issue could be that the function is not deployed yet because of a circular dependency. CloudFormation may be trying to invoke the function before it is created. Option C is correct. Option A is wrong because the ARN is correct. Option B is wrong because IAM permissions would cause a different error. Option D is wrong because the function exists.
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 Lambda function is defined in the same template and has a circular dependency
Why this is correct
CloudFormation cannot use a resource that is being created in the same stack as a custom resource without proper DependsOn
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 Lambda function is not in the same AWS region
Why it's wrong here
The ARN shows us-east-1, same as the stack
✗
The Lambda function lacks necessary IAM permissions
Why it's wrong here
Permissions issue would show an access denied error
✗
The Lambda function ARN is malformed
Why it's wrong here
The ARN appears correctly formatted
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
The ARN shows us-east-1, same as the stack
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 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.
Identify which DOP-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.
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Lambda function is defined in the same template and has a circular dependency — The error indicates that CloudFormation cannot find the Lambda function. Since the function exists in the same account and region, the issue could be that the function is not deployed yet because of a circular dependency. CloudFormation may be trying to invoke the function before it is created. Option C is correct. Option A is wrong because the ARN is correct. Option B is wrong because IAM permissions would cause a different error. Option D is wrong because the function exists.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-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.
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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