The correct answer is to associate a customer-managed KMS key with the log group and update the key policy to allow CloudWatch Logs to use it. This is required because CloudWatch Logs encryption at rest with a customer-managed KMS key is not automatic; the service needs explicit permissions in the key policy to perform cryptographic operations like kms:Encrypt, kms:Decrypt, kms:ReEncrypt*, kms:GenerateDataKey*, and kms:DescribeKey. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding that simply specifying a KMS key ID on a log group is insufficient—the key policy must grant CloudWatch Logs principal access, or encryption will fail silently. A common trap is assuming the default AWS managed key works without policy changes, but customer-managed keys require this explicit update. Memory tip: think “Logs need the key’s permission slip”—without the policy grant, CloudWatch Logs cannot touch the key.
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 CloudWatch Logs to store application logs. The security team requires that logs be encrypted at rest using a customer-managed KMS key. What must be done to enable this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Associate a customer-managed KMS key with the log group and update the key policy to allow CloudWatch Logs to use it.
Option D is correct because CloudWatch Logs supports encryption at rest using a customer-managed KMS key. To enable this, you must associate the KMS key with the log group via the CloudWatch Logs console or API, and you must update the key policy to grant CloudWatch Logs the necessary permissions (kms:Encrypt, kms:Decrypt, kms:ReEncrypt*, kms:GenerateDataKey*, and kms:DescribeKey). Without this key policy update, CloudWatch Logs cannot use the key to encrypt the log data at rest.
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.
✗
Enable encryption on the log group using the default AWS managed key.
Why it's wrong here
Default key is not customer-managed.
✗
Use a third-party encryption tool before sending logs to CloudWatch.
Why it's wrong here
CloudWatch Logs natively supports KMS encryption.
✗
Create a new log group in a region where KMS is enabled.
Why it's wrong here
KMS is available in all regions.
✓
Associate a customer-managed KMS key with the log group and update the key policy to allow CloudWatch Logs to use it.
Why this is correct
Associating a CMK and updating the key policy enables encryption.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume encryption is automatically applied when a KMS key exists in the account, but they overlook the critical step of updating the key policy to grant CloudWatch Logs service principal permissions to use the key.
Detailed technical explanation
How to think about this question
Under the hood, when you associate a customer-managed KMS key with a log group, CloudWatch Logs uses envelope encryption: it calls GenerateDataKey to get a data key encrypted by the KMS key, uses that data key to encrypt log events, and stores the encrypted data key alongside the log data. A subtle behavior is that once encryption is enabled on a log group, it cannot be disabled or changed to a different key; you must create a new log group if you need to change the key. In a real-world scenario, if the KMS key is deleted or disabled, CloudWatch Logs will fail to decrypt log data for retrieval, leading to data loss.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Associate a customer-managed KMS key with the log group and update the key policy to allow CloudWatch Logs to use it. — Option D is correct because CloudWatch Logs supports encryption at rest using a customer-managed KMS key. To enable this, you must associate the KMS key with the log group via the CloudWatch Logs console or API, and you must update the key policy to grant CloudWatch Logs the necessary permissions (kms:Encrypt, kms:Decrypt, kms:ReEncrypt*, kms:GenerateDataKey*, and kms:DescribeKey). Without this key policy update, CloudWatch Logs cannot use the key to encrypt the log data at rest.
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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Question Discussion
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