This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
An IAM policy is attached to a data engineering role that writes to an S3 bucket. The policy is shown in the exhibit. What is the effect of this policy?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The role must use SSE-KMS when writing objects; reading is allowed only if the object is encrypted with SSE-KMS
The IAM policy uses a `Condition` block with `s3:x-amz-server-side-encryption` set to `aws:kms`, which enforces that any `PutObject` request must include SSE-KMS encryption. The `Deny` effect on `s3:GetObject` when encryption is not `aws:kms` ensures that reading objects without SSE-KMS is blocked. This combination allows writing only with SSE-KMS and reading only of objects encrypted with SSE-KMS, making option D correct.
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.
✗
The role can write objects with any encryption, but reading is restricted to SSE-KMS only
Why it's wrong here
The Deny statement prevents writing without SSE-KMS.
✗
The role can read and write any object without encryption restrictions
Why it's wrong here
The policy restricts both read and write to SSE-KMS encrypted objects.
✗
The role can only read objects; writing is always denied
Why it's wrong here
The first statement allows PutObject with SSE-KMS, so writing is not always denied.
✓
The role must use SSE-KMS when writing objects; reading is allowed only if the object is encrypted with SSE-KMS
Why this is correct
The Allow statement grants GetObject only when SSE-KMS is specified, and the Deny statement enforces SSE-KMS for PutObject.
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 overlook the `Deny` effect on `s3:GetObject` and assume the policy only restricts writes, missing that reading is also conditionally denied unless the object uses SSE-KMS.
Detailed technical explanation
How to think about this question
The `s3:x-amz-server-side-encryption` condition key checks the `x-amz-server-side-encryption` header in the request, which must be set to `aws:kms` for SSE-KMS. The `Deny` effect in the policy overrides any `Allow` statements, ensuring that non-compliant requests are blocked even if other policies grant broader access. In practice, this enforces a data-at-rest encryption requirement for both read and write operations, which is common in regulated environments like healthcare or finance.
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.
Quick reference
AWS S3 Storage Class Comparison
Storage Class
Min Duration
Retrieval
Use Case
S3 Standard
None
Immediate
Frequently accessed data
S3 Standard-IA
30 days
Immediate
Infrequent access, rapid retrieval
S3 One Zone-IA
30 days
Immediate
Non-critical infrequent data
S3 Intelligent-Tiering
None
Immediate–hours
Unknown or changing access patterns
S3 Glacier Instant
90 days
Milliseconds
Archive with instant retrieval
S3 Glacier Flexible
90 days
Minutes–hours
Archive, flexible retrieval
S3 Glacier Deep Archive
180 days
Hours
Long-term compliance archive
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.
Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The role must use SSE-KMS when writing objects; reading is allowed only if the object is encrypted with SSE-KMS — The IAM policy uses a `Condition` block with `s3:x-amz-server-side-encryption` set to `aws:kms`, which enforces that any `PutObject` request must include SSE-KMS encryption. The `Deny` effect on `s3:GetObject` when encryption is not `aws:kms` ensures that reading objects without SSE-KMS is blocked. This combination allows writing only with SSE-KMS and reading only of objects encrypted with SSE-KMS, making option D correct.
What should I do if I get this MLS-C01 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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