This MLS-C01 practice question tests your understanding of exploratory data analysis. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: kMS encryption for S3. 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 data scientist creates the above IAM policy and attaches it to a role used by an Amazon SageMaker notebook instance. When trying to save a file to the S3 bucket, the operation fails. What is the missing permission?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
kms:GenerateDataKey
The correct answer is C (kms:GenerateDataKey) because the S3 bucket is likely encrypted with a KMS key. When SageMaker writes an object to an encrypted bucket, it needs permission to call kms:GenerateDataKey to generate a data key for encryption. Option A (kms:Decrypt) is for decryption, not encryption. Option B (s3:ListBucket) allows listing objects, not writing. Option D (s3:GetObject) allows reading objects, not writing. The error when saving indicates missing encryption permissions.
Key principle: KMS encryption for S3
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
kms:Decrypt
Why it's wrong here
Decrypt is for reading encrypted objects.
✗
s3:ListBucket
Why it's wrong here
ListBucket is for listing objects, not writing.
✓
kms:GenerateDataKey
Why this is correct
If the bucket uses SSE-KMS, PutObject requires kms:GenerateDataKey to encrypt the object.
Related concept
KMS encryption for S3
✗
s3:GetObject
Why it's wrong here
GetObject is for reading.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The missing permission is often kms:GenerateDataKey for writing to KMS-encrypted buckets, not s3:PutObject which is already granted.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
KMS encryption for S3
Required permissions for writing to S3
Common misstep
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
KMS encryption for S3
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
Review kMS encryption for S3, then practise related MLS-C01 questions on the same topic to reinforce the concept.
Exploratory Data Analysis — This question tests Exploratory Data Analysis — KMS encryption for S3.
What is the correct answer to this question?
The correct answer is: kms:GenerateDataKey — The correct answer is C (kms:GenerateDataKey) because the S3 bucket is likely encrypted with a KMS key. When SageMaker writes an object to an encrypted bucket, it needs permission to call kms:GenerateDataKey to generate a data key for encryption. Option A (kms:Decrypt) is for decryption, not encryption. Option B (s3:ListBucket) allows listing objects, not writing. Option D (s3:GetObject) allows reading objects, not writing. The error when saving indicates missing encryption permissions.
What should I do if I get this MLS-C01 question wrong?
Review kMS encryption for S3, then practise related MLS-C01 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
KMS encryption for S3
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Question Discussion
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