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Question 724 of 1,616

Security →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is to add a statement granting kms:Decrypt to the Lambda function's execution role in the KMS key policy. This is correct because KMS key policies are resource-based policies that act as the primary access control for the key itself; even if an IAM policy attached to the role allows kms:Decrypt, that permission is ineffective unless the key policy explicitly authorizes the role (or the account) to perform the action. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of the interaction between identity-based and resource-based policies—a common trap is assuming IAM permissions alone are sufficient for KMS operations. Remember that KMS requires explicit permission from both the key policy and the IAM policy unless the key policy grants full access to the account. Memory tip: "Key policy is the gatekeeper—IAM permission gets you to the gate, but the key policy must open it."

DVA-C02 Security Practice Question

This DVA-C02 practice question tests your understanding of security. 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 a customer managed AWS KMS key to encrypt sensitive data stored in DynamoDB. A Lambda function reads from the DynamoDB table and needs to decrypt the data. The Lambda function's execution role has an IAM policy that allows kms:Decrypt on the key. However, access is denied. What must the developer add to the KMS key policy to resolve the issue?

Question 1hardmultiple choice

Full question →

A
Add a statement granting kms:Decrypt to the Lambda function's execution role.
Correct. The key policy must explicitly allow the IAM role to perform kms:Decrypt.
B
Add a statement granting kms:Decrypt to the Lambda function's resource-based policy.
Why wrong: Lambda functions do not have resource-based policies for KMS; the key policy is the resource policy.
C
Add a statement granting kms:Decrypt to the Lambda service principal.
Why wrong: The service principal is not the entity that accesses the key; the execution role does.
D
Add a statement granting kms:Decrypt to the account root user with a condition for the Lambda function.
Why wrong: While the root user can delegate access via IAM, a condition on the root is not a secure or direct way to grant the Lambda role.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Add a statement granting kms:Decrypt to the Lambda function's execution role.

The correct answer is A because KMS key policies are resource-based policies that control access to the key itself. Even if the Lambda execution role has an IAM policy granting kms:Decrypt, the KMS key policy must explicitly allow the role (or the user/account) to perform that action. Without this statement in the key policy, the IAM permission is ineffective, resulting in an access denied error.

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.

✓
Add a statement granting kms:Decrypt to the Lambda function's execution role.
Why this is correct
Correct. The key policy must explicitly allow the IAM role to perform kms:Decrypt.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a statement granting kms:Decrypt to the Lambda function's resource-based policy.
Why it's wrong here
Lambda functions do not have resource-based policies for KMS; the key policy is the resource policy.
✗
Add a statement granting kms:Decrypt to the Lambda service principal.
Why it's wrong here
The service principal is not the entity that accesses the key; the execution role does.
✗
Add a statement granting kms:Decrypt to the account root user with a condition for the Lambda function.
Why it's wrong here
While the root user can delegate access via IAM, a condition on the root is not a secure or direct way to grant the Lambda role.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume IAM permissions alone are sufficient for KMS operations, forgetting that KMS key policies act as an additional layer of access control that must explicitly allow the principal.

Detailed technical explanation

How to think about this question

AWS KMS uses a combination of key policies and IAM policies to control access. When a key policy does not explicitly grant access to a principal, IAM policies alone are insufficient unless the key policy delegates authority to the account (by setting a default key policy that allows IAM policies to take effect). In this scenario, the key is customer managed, so the key policy must include a statement allowing the Lambda execution role to call kms:Decrypt. The kms:Decrypt action is required because DynamoDB stores data encrypted at rest, and the Lambda function must decrypt it after reading the ciphertext.

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.

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FAQ

Questions learners often ask

What does this DVA-C02 question test?

Security — This question tests Security — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Add a statement granting kms:Decrypt to the Lambda function's execution role. — The correct answer is A because KMS key policies are resource-based policies that control access to the key itself. Even if the Lambda execution role has an IAM policy granting kms:Decrypt, the KMS key policy must explicitly allow the role (or the user/account) to perform that action. Without this statement in the key policy, the IAM permission is ineffective, resulting in an access denied error.

What should I do if I get this DVA-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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This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.