- A
S3 versioning is not enabled on the bucket.
S3 versioning is not enabled on the bucket. This is the most likely cause because CodePipeline's S3 source action relies on versioning to detect new uploads. Without versioning, the pipeline cannot reliably associate the event notification with a specific object version, preventing the pipeline from starting.
- B
The pipeline execution role does not have permission to read from the S3 bucket.
Why wrong: This would affect pipeline execution, not triggering.
- C
The Lambda function does not have permission to start the pipeline.
Why wrong: This would cause an error, but the question says the pipeline is not triggering, implying no invocation.
- D
The S3 bucket does not have a bucket policy that allows S3 to invoke Lambda.
Why wrong: S3 can invoke Lambda with proper permissions, but bucket policy is not required.
Why CodePipeline S3 Source Trigger Fails: Enable Versioning
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 CodePipeline to automate deployments. The pipeline source stage uses Amazon S3. The developer wants to automatically trigger the pipeline when a new version of the source file is uploaded. The developer has configured S3 event notifications to invoke a Lambda function that starts the pipeline. However, the pipeline is not triggering. 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 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
S3 versioning is not enabled on the bucket.
The most likely cause is that S3 versioning is not enabled on the bucket. When S3 event notifications are used to trigger a Lambda function that starts a pipeline, the pipeline source action must be configured to detect changes in the S3 bucket. Without versioning enabled, CodePipeline cannot reliably track which object version triggered the event, and the pipeline may not start because the source action expects version IDs to identify changes. Enabling versioning ensures that each upload creates a unique version ID, allowing CodePipeline to properly detect and respond to new uploads.
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.
- ✓
S3 versioning is not enabled on the bucket.
Why this is correct
S3 versioning is not enabled on the bucket. This is the most likely cause because CodePipeline's S3 source action relies on versioning to detect new uploads. Without versioning, the pipeline cannot reliably associate the event notification with a specific object version, preventing the pipeline from starting.
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 pipeline execution role does not have permission to read from the S3 bucket.
Why it's wrong here
This would affect pipeline execution, not triggering.
- ✗
The Lambda function does not have permission to start the pipeline.
Why it's wrong here
This would cause an error, but the question says the pipeline is not triggering, implying no invocation.
- ✗
The S3 bucket does not have a bucket policy that allows S3 to invoke Lambda.
Why it's wrong here
S3 can invoke Lambda with proper permissions, but bucket policy is not required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often overlook the requirement for S3 versioning in CodePipeline source actions, mistakenly focusing on permissions or Lambda invocation policies instead of the fundamental detection mechanism.
Detailed technical explanation
How to think about this question
Under the hood, CodePipeline's S3 source action uses the S3 object version ID to detect changes. When versioning is disabled, S3 overwrites the object with the same key, and the version ID remains null or unchanged, so CodePipeline cannot differentiate between the old and new object. This is a common misconfiguration because developers often assume S3 event notifications alone are sufficient, but CodePipeline requires versioning to correlate events with specific object versions. In real-world scenarios, this issue also affects pipelines using S3 as a source for CI/CD, where multiple uploads of the same file without versioning lead to missed triggers.
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.
TExam Day Tips
- 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.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
What to study next
Got this wrong? Here's your next step.
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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: S3 versioning is not enabled on the bucket. — The most likely cause is that S3 versioning is not enabled on the bucket. When S3 event notifications are used to trigger a Lambda function that starts a pipeline, the pipeline source action must be configured to detect changes in the S3 bucket. Without versioning enabled, CodePipeline cannot reliably track which object version triggered the event, and the pipeline may not start because the source action expects version IDs to identify changes. Enabling versioning ensures that each upload creates a unique version ID, allowing CodePipeline to properly detect and respond to new uploads.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Jul 4, 2026
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