- A
The custom resource Lambda function has not been updated with the new code; the stack is using a previous version of the function.
If the Lambda function code is changed but the stack uses the old version, it will return the same identifier.
- B
The stack is using the same stack name, and CloudFormation is reusing the previous custom resource output.
Why wrong: CloudFormation does not reuse custom resource outputs across stack creations.
- C
The custom resource Lambda function is returning the same value because it uses a random number generator without a seed.
Why wrong: Random generators should produce different values each time, but the issue is likely caching.
- D
The custom resource Lambda function is not being invoked during stack creation because the service token is incorrect.
Why wrong: If the token were incorrect, the stack would fail with a different error.
DVA-C02 Deployment Practice Question
This DVA-C02 practice question tests your understanding of deployment. 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 infrastructure. The developer has created a stack that includes an Amazon RDS DB instance. The stack creation fails with a rollback, and the error message indicates that the DB instance could not be created because the DB instance identifier already exists. The developer has verified that there is no existing DB instance with that identifier in the account. The stack uses a custom resource to generate the DB instance identifier. The custom resource is a Lambda function that returns a unique identifier. The developer suspects that the custom resource is returning a stale value. What is the MOST likely cause of this issue?
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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The custom resource Lambda function has not been updated with the new code; the stack is using a previous version of the function.
Option D is correct because custom resources in CloudFormation can return data that is cached if the Lambda function is not updated correctly. The developer may have updated the Lambda function code but the stack is still using the old function version. Option A is incorrect because the custom resource is invoked each time the stack is created; it should generate a new value. Option B is incorrect because if the custom resource is not invoked, the stack would fail with a different error (missing property). Option C is incorrect because the DB instance identifier is generated by the custom resource, not by the stack name.
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 custom resource Lambda function has not been updated with the new code; the stack is using a previous version of the function.
Why this is correct
If the Lambda function code is changed but the stack uses the old version, it will return the same identifier.
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 is using the same stack name, and CloudFormation is reusing the previous custom resource output.
Why it's wrong here
CloudFormation does not reuse custom resource outputs across stack creations.
- ✗
The custom resource Lambda function is returning the same value because it uses a random number generator without a seed.
Why it's wrong here
Random generators should produce different values each time, but the issue is likely caching.
- ✗
The custom resource Lambda function is not being invoked during stack creation because the service token is incorrect.
Why it's wrong here
If the token were incorrect, the stack would fail with a different error.
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
CloudFormation does not reuse custom resource outputs across stack creations.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which DVA-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
Questions learners often ask
What does this DVA-C02 question test?
Deployment — This question tests Deployment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The custom resource Lambda function has not been updated with the new code; the stack is using a previous version of the function. — Option D is correct because custom resources in CloudFormation can return data that is cached if the Lambda function is not updated correctly. The developer may have updated the Lambda function code but the stack is still using the old function version. Option A is incorrect because the custom resource is invoked each time the stack is created; it should generate a new value. Option B is incorrect because if the custom resource is not invoked, the stack would fail with a different error (missing property). Option C is incorrect because the DB instance identifier is generated by the custom resource, not by the stack name.
What should I do if I get this DVA-C02 question wrong?
Identify which DVA-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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Last reviewed: Jun 20, 2026
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