The correct answer is to add a branch filter in the CloudWatch Events rule that triggers the pipeline, specifying only the main branch. This works because CodePipeline relies on Amazon CloudWatch Events to detect source changes from CodeCommit; by default, the rule pattern matches all branch events, so feature branch merges also fire the pipeline. Adding a branch filter narrows the event pattern to only the main branch, ensuring that only direct commits to main trigger the pipeline. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of event-driven pipeline orchestration and the common trap of forgetting that CloudWatch Events rules are broad unless explicitly filtered. A key memory tip is to think of CloudWatch Events as the gatekeeper: without a branch filter, it lets every branch through, so you must lock the gate to the main branch only.
DOP-C02 Restrict CodePipeline to main branch Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 DevOps engineer is designing a CI/CD pipeline using AWS CodePipeline. The source stage is AWS CodeCommit, and the build stage uses AWS CodeBuild. The pipeline must only trigger on changes to the main branch. However, the engineer notices that the pipeline is also triggering on changes to feature branches that are merged via pull requests. What configuration change should the engineer make to ensure the pipeline only triggers on direct commits to the main branch?
Configure the CodeCommit repository to disable events for all branches except main.
Why wrong: CodeCommit does not have a per-branch event setting; events are emitted for all branches.
C
Modify the pipeline's source stage to use a branch name filter, which will ignore events from other branches.
Why wrong: The branch name in the source action only defines which branch to pull; the trigger event still comes from any branch unless filtered at the event rule.
D
Use a Lambda function as a source action to check the branch before starting the build.
Why wrong: This is a workaround but not the standard or efficient solution; the event rule filter is simpler.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a branch filter in the CloudWatch Events rule that triggers the pipeline, specifying only the main branch.
Option B is correct because AWS CodePipeline pipelines are triggered by CloudWatch Events rules that monitor CodeCommit repository events. By default, the rule may trigger on all branch changes. Adding a branch filter in the CloudWatch Events rule that specifies only the main branch ensures that only direct commits to main trigger the pipeline, ignoring feature branch merges.
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.
✗
Configure the CodeCommit repository to disable events for all branches except main.
Why it's wrong here
CodeCommit does not have a per-branch event setting; events are emitted for all branches.
✗
Modify the pipeline's source stage to use a branch name filter, which will ignore events from other branches.
Why it's wrong here
The branch name in the source action only defines which branch to pull; the trigger event still comes from any branch unless filtered at the event rule.
✗
Use a Lambda function as a source action to check the branch before starting the build.
Why it's wrong here
This is a workaround but not the standard or efficient solution; the event rule filter is simpler.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The DOP-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓Add a branch filter in the CloudWatch Events rule that triggers the pipeline, specifying only the main branch.Correct answer▾✗Configure the CodeCommit repository to disable events for all branches except main.Wrong answer — click to see why▾
Why this is wrong here
CodeCommit does not have a per-branch event setting; events are emitted for all branches.
✗Modify the pipeline's source stage to use a branch name filter, which will ignore events from other branches.Wrong answer — click to see why▾
Why this is wrong here
The branch name in the source action only defines which branch to pull; the trigger event still comes from any branch unless filtered at the event rule.
✗Use a Lambda function as a source action to check the branch before starting the build.Wrong answer — click to see why▾
Why this is wrong here
This is a workaround but not the standard or efficient solution; the event rule filter is simpler.
Analysis generated from the official DOP-C02blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the pipeline source stage branch filter (which only affects which branch is used as source code) with the CloudWatch Events rule branch filter (which controls which events actually trigger the pipeline), leading them to incorrectly select option C.
Detailed technical explanation
How to think about this question
Under the hood, CodePipeline uses Amazon CloudWatch Events (now Amazon EventBridge) to capture CodeCommit repository state changes via the 'codecommit:GitReferenceUpdate' event. The event rule can include a 'referenceType' and 'referenceName' filter to match only branch updates. Without the filter, the rule matches all branch updates, causing the pipeline to trigger on any push, including merges. In real-world scenarios, this is critical to avoid unnecessary builds and cost from feature branch activity.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Add a branch filter in the CloudWatch Events rule that triggers the pipeline, specifying only the main branch. — Option B is correct because AWS CodePipeline pipelines are triggered by CloudWatch Events rules that monitor CodeCommit repository events. By default, the rule may trigger on all branch changes. Adding a branch filter in the CloudWatch Events rule that specifies only the main branch ensures that only direct commits to main trigger the pipeline, ignoring feature branch merges.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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