The answer is a combination of IAM policies and a key policy that limits key administrators and key users. This is correct because to prevent unauthorized KMS key use, you must apply a defense-in-depth approach: IAM policies restrict the `kms:Decrypt` action to only the specific IAM roles that need it for the claims portal, while the key policy explicitly defines who can manage or use the key, acting as a resource-based control that overrides any broader IAM permissions. On the SAA-C03 exam, this tests your understanding that KMS requires both identity-based and resource-based policies to work together—a common trap is assuming an IAM policy alone is sufficient, but without a key policy that denies access by default, any principal with S3 object access could still decrypt the data. Remember the mnemonic "IAM for who, Key Policy for what"—IAM controls which principals can act, while the key policy controls what actions are allowed on the key itself.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure architectures. 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 is encrypting sensitive S3 data for a claims portal with AWS KMS. Which two controls help prevent accidental use of the KMS key by unauthorized principals?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
IAM policies that grant kms:Decrypt only to required application roles
Option B is correct because IAM policies can be used to restrict the `kms:Decrypt` action to only the specific IAM roles that require it for the claims portal. This ensures that even if an unauthorized principal has access to the encrypted S3 object, they cannot decrypt it without the explicit IAM permission to use the KMS key. Option C is correct because a key policy that explicitly defines key administrators and key users limits who can manage or use the KMS key, preventing accidental use by unauthorized principals.
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.
✗
A larger KMS key rotation period
Why it's wrong here
Rotation interval does not determine which principals may use a key.
✓
IAM policies that grant kms:Decrypt only to required application roles
Why this is correct
IAM permissions should grant least-privilege use of the KMS key to specific roles.
Related concept
Read the scenario before looking for a memorised answer.
✓
A key policy that limits key administrators and key users
Why this is correct
The KMS key policy is the primary resource policy that controls who can administer or use the key.
Related concept
Read the scenario before looking for a memorised answer.
✗
S3 Transfer Acceleration
Why it's wrong here
Transfer Acceleration does not control KMS key usage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume that IAM policies alone are sufficient to control KMS key access, but they forget that the key policy must also explicitly allow the IAM principal to use the key, as KMS requires both the key policy and IAM policy to grant access.
Detailed technical explanation
How to think about this question
KMS key policies are resource-based policies that define who can use the key (key users) and who can administer it (key administrators). IAM policies can further refine permissions for principals that are already allowed by the key policy, but they cannot grant access that the key policy denies. In this scenario, combining a restrictive key policy with IAM policies that limit `kms:Decrypt` to specific application roles ensures that only the claims portal's compute role can decrypt the sensitive data, even if other principals have access to the S3 bucket.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: IAM policies that grant kms:Decrypt only to required application roles — Option B is correct because IAM policies can be used to restrict the `kms:Decrypt` action to only the specific IAM roles that require it for the claims portal. This ensures that even if an unauthorized principal has access to the encrypted S3 object, they cannot decrypt it without the explicit IAM permission to use the KMS key. Option C is correct because a key policy that explicitly defines key administrators and key users limits who can manage or use the KMS key, preventing accidental use by unauthorized principals.
What should I do if I get this SAA-C03 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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is encrypting sensitive S3 data for a IoT ingestion API with AWS KMS. Which two controls help prevent accidental use of the KMS key by unauthorized principals? The design must avoid adding custom operational scripts.
hard
✓ A.IAM policies that grant kms:Decrypt only to required application roles
B.S3 Transfer Acceleration
✓ C.A key policy that limits key administrators and key users
D.A larger KMS key rotation period
Why A: Option A is correct because IAM policies can explicitly grant kms:Decrypt only to specific application roles, ensuring that only authorized principals (e.g., the IoT ingestion service role) can use the KMS key for decryption. This prevents unauthorized principals from accidentally or maliciously decrypting S3 objects, as the policy restricts the action to required roles without needing custom scripts.
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This SAA-C03 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 SAA-C03 exam.
Question Discussion
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