This DBS-C01 practice question tests your understanding of deployment and migration. 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.
Refer to the exhibit. A company is creating an Aurora MySQL cluster using the AWS CLI. The command fails with an error. The company has a default KMS key but the command specifies a customer-managed KMS key. What is the most likely cause of the failure?
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.
The IAM user does not have permission to use the specified KMS key
Permission to use the KMS key is required.
The --kms-key-id parameter is not supported for aurora-mysql engine
Why wrong: The parameter is supported for Aurora MySQL.
The KMS key does not exist
Why wrong: The key is specified as existing, but permissions may be missing.
The KMS key is in a different region
Why wrong: Cross-region KMS keys can be used, but the issue is likely permissions.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The IAM user does not have permission to use the specified KMS key
The most likely cause of the failure is that the IAM user does not have the required permissions to use the specified customer-managed KMS key. When you specify a KMS key in the `--kms-key-id` parameter for an Aurora MySQL cluster, the IAM user must have `kms:CreateGrant`, `kms:Decrypt`, and `kms:Encrypt` permissions on that key. If the user lacks these permissions, the command fails even if the key exists and is in the correct region.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The IAM user does not have permission to use the specified KMS key
Why this is correct
Permission to use the KMS key is required.
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 --kms-key-id parameter is not supported for aurora-mysql engine
Why it's wrong here
The parameter is supported for Aurora MySQL.
The KMS key does not exist
Why it's wrong here
The key is specified as existing, but permissions may be missing.
The KMS key is in a different region
Why it's wrong here
Cross-region KMS keys can be used, but the issue is likely permissions.
Common exam traps
The trap here is that candidates often assume the error is due to the key not existing or being in a different region, but the most common failure is an IAM permissions issue on the KMS key, especially when a customer-managed key is specified instead of the default AWS managed key.
Detailed technical explanation
Under the hood, when you create an encrypted Aurora cluster with a customer-managed KMS key, the AWS CLI calls the `CreateDBCluster` API, which triggers a `kms:CreateGrant` to allow the Aurora service to use the key on your behalf. If the IAM user lacks `kms:CreateGrant`, the API call fails with an `AccessDeniedException`. In real-world scenarios, this often happens when using a key from another account or when the key's key policy does not grant the necessary permissions to the IAM user or role.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
The correct answer is: The IAM user does not have permission to use the specified KMS key — The most likely cause of the failure is that the IAM user does not have the required permissions to use the specified customer-managed KMS key. When you specify a KMS key in the `--kms-key-id` parameter for an Aurora MySQL cluster, the IAM user must have `kms:CreateGrant`, `kms:Decrypt`, and `kms:Encrypt` permissions on that key. If the user lacks these permissions, the command fails even if the key exists and is in the correct region.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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