The correct answer is to use a customer managed AWS KMS key with a key policy that allows access from all accounts in the organization. This works because cross-account KMS key access is governed solely by the key policy, not by S3 bucket policies or IAM permissions alone; the key policy must explicitly grant the encrypt and decrypt actions to the root users or roles of the target accounts within the AWS Organization. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding that for cross-account S3 data lake encryption, you must decouple the key management from the bucket policy—a common trap is assuming an S3 bucket policy can authorize KMS operations, but it cannot. Remember the memory tip: “Key policy for keys, bucket policy for buckets.”
SAP-C02 Practice Question: Design Solutions for Organizational Complexity
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. 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 implementing a data lake on Amazon S3. The data lake must be accessible from multiple accounts within the same AWS Organization. Objects must be encrypted at rest, and the company wants to use a single AWS KMS key for simplicity. Which solution meets these requirements?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a customer managed AWS KMS key with a key policy that allows access from all accounts in the organization.
Option C is correct because a multi-region key is not needed, and cross-account access requires key policy. Option A is wrong because SSE-S3 does not allow cross-account access control. Option B is wrong because SSE-C requires managing keys externally. Option D is wrong because S3 bucket policies cannot grant access to KMS keys.
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.
✗
Use SSE-S3 encryption. Grant cross-account access via bucket policy.
Why it's wrong here
SSE-S3 does not support cross-account access to objects encrypted with it; the caller needs KMS permissions.
✗
Use SSE-C encryption. Provide the same customer key to all accounts.
Why it's wrong here
Requires key distribution and management overhead.
✓
Use a customer managed AWS KMS key with a key policy that allows access from all accounts in the organization.
Why this is correct
Allows centralized key management and cross-account access via key policy.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use SSE-KMS with a key per account and use S3 bucket policy to allow cross-account access.
Why it's wrong here
Multiple keys add complexity; bucket policy does not grant KMS decrypt permissions.
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 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 SAP-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.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a customer managed AWS KMS key with a key policy that allows access from all accounts in the organization. — Option C is correct because a multi-region key is not needed, and cross-account access requires key policy. Option A is wrong because SSE-S3 does not allow cross-account access control. Option B is wrong because SSE-C requires managing keys externally. Option D is wrong because S3 bucket policies cannot grant access to KMS keys.
What should I do if I get this SAP-C02 question wrong?
Identify which SAP-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.
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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