The most likely reason is that the IAM role for the EC2 instance lacks the kms:Encrypt permission. CloudWatch Logs uses a service-linked IAM role to write logs, and when a customer-managed KMS key (CMK) is associated with a log group, that role must explicitly be granted kms:Encrypt and kms:GenerateDataKey permissions in the key policy or via an IAM policy; without these, the logs are delivered but remain unencrypted. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of the interplay between KMS key policies and IAM roles—a common trap is assuming encryption is configured at the CloudWatch agent level, but it is actually applied at the log group level. Remember: the agent delivers plaintext logs, and the encryption handshake happens between CloudWatch Logs and KMS, so the service role, not the instance role, needs the encrypt permission. Memory tip: “Logs land, but KMS demands a hand—check the service role’s encrypt command.”
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 uses Amazon CloudWatch Logs to collect application logs from EC2 instances. The security team requires that log data be encrypted at rest using a customer-managed AWS KMS key. The logs are currently being delivered, but they are not encrypted. 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 IAM role for the EC2 instance does not have kms:Encrypt permission
Option C is correct because the CloudWatch Logs role must have kms:Encrypt permission to use CMK. Option A is wrong because KMS key policies allow IAM policies but IAM policies must grant permissions. Option B is wrong because the CMK must be enabled, but that's not the typical issue. Option D is wrong because encryption is applied at log group level, not at the agent level.
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 IAM role for the EC2 instance does not have kms:Encrypt permission
Why this is correct
The role needs permission to encrypt using the CMK.
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 CloudWatch Logs agent is not configured to encrypt logs
Why it's wrong here
Encryption is set at the log group level, not agent.
✗
The KMS key is disabled
Why it's wrong here
If disabled, no logs would be delivered.
✗
The KMS key policy does not allow the CloudWatch Logs service principal
Why it's wrong here
The key policy must allow CloudWatch Logs to use the key, but the question says role not attached.
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 IAM role for the EC2 instance does not have kms:Encrypt permission — Option C is correct because the CloudWatch Logs role must have kms:Encrypt permission to use CMK. Option A is wrong because KMS key policies allow IAM policies but IAM policies must grant permissions. Option B is wrong because the CMK must be enabled, but that's not the typical issue. Option D is wrong because encryption is applied at log group level, not at the agent level.
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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