The answer is that the AWS Config custom rule is not configured to trigger on AWS::EC2::Instance resources. This is the most likely reason because AWS Config rules must have their scope explicitly set to the resource type they are meant to evaluate; without specifying AWS::EC2::Instance in the rule’s configuration, the rule will not react to EC2 launch events, even if it is set to evaluate on configuration changes. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how AWS Config rule scoping works—a common trap is assuming that a rule will automatically apply to all resources, when in fact you must define the resource type in the rule’s triggers. A helpful memory tip is “scope before trigger”: always verify that the rule’s scope includes the exact resource type you want to monitor, or the Lambda function will never be invoked.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. 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's DevOps team uses AWS Config to monitor resource compliance. They have created a custom AWS Config rule that triggers an AWS Lambda function to evaluate whether EC2 instances have the 'Environment' tag with value 'Production' or 'Staging'. The rule is set to evaluate resources on configuration changes. However, the team notices that the rule does not trigger when an EC2 instance is launched. The Lambda function's IAM role has the necessary permissions to describe EC2 instances. The CloudWatch Logs for the Lambda function show that it is not being invoked. What is the MOST likely reason?
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 AWS Config rule is not configured to trigger on AWS::EC2::Instance resources.
Option A is correct because AWS Config rules need to be associated with the specific resource type (AWS::EC2::Instance) in the rule's scope; without this, the rule won't trigger on EC2 instance changes. Option B is wrong because the Lambda function's permissions are sufficient; the issue is before invocation. Option C is wrong because the rule is event-based; evaluation on configuration changes should work. Option D is wrong because a custom rule can be triggered by configuration changes.
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's IAM role does not have permission to write to CloudWatch Logs.
Why it's wrong here
The function is not being invoked, so permission to write logs is not the issue.
✗
The AWS Config rule is set to evaluate resources periodically, not on configuration changes.
Why it's wrong here
The stem says it is set to evaluate on configuration changes, which should trigger on launch.
✓
The AWS Config rule is not configured to trigger on AWS::EC2::Instance resources.
Why this is correct
The rule's scope must include the resource type; otherwise, Config will not evaluate EC2 instances.
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 custom rule must be deployed using AWS CloudFormation to be active.
Why it's wrong here
Custom rules can be created via Console, CLI, or SDK; CloudFormation is not required.
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.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The AWS Config rule is not configured to trigger on AWS::EC2::Instance resources. — Option A is correct because AWS Config rules need to be associated with the specific resource type (AWS::EC2::Instance) in the rule's scope; without this, the rule won't trigger on EC2 instance changes. Option B is wrong because the Lambda function's permissions are sufficient; the issue is before invocation. Option C is wrong because the rule is event-based; evaluation on configuration changes should work. Option D is wrong because a custom rule can be triggered by configuration changes.
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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