SageMaker Training Job: Missing s3:ListBucket Permission
This MLS-C01 practice question tests your understanding of modeling. 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 data scientist has this IAM policy attached to an IAM role used by SageMaker. When trying to create a training job, the scientist gets an access denied error. The training data is in 's3://my-bucket/training-data/'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Missing s3:ListBucket permission
The error occurs because the IAM policy grants s3:GetObject permission on the training data objects but lacks s3:ListBucket permission on the bucket itself. SageMaker's CreateTrainingJob API first performs a ListBucket call to verify the bucket exists and to enumerate objects, even if the exact object key is known. Without s3:ListBucket, the ListBucket call fails, 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.
✗
The bucket name is misspelled
Why it's wrong here
The bucket name matches.
✗
The S3 resource ARN is incorrect
Why it's wrong here
The ARN matches the bucket and prefix.
✓
Missing s3:ListBucket permission
Why this is correct
SageMaker needs ListBucket permission to access objects.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The sagemaker:CreateTrainingJob action is not allowed
Why it's wrong here
It is allowed with Resource '*'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The MLS-C01 exam often tests the misconception that only s3:GetObject is needed to read objects from S3, but SageMaker's training job creation also requires s3:ListBucket to validate the bucket, making the missing ListBucket permission a common trap.
Detailed technical explanation
How to think about this question
SageMaker's CreateTrainingJob API requires both s3:GetObject (to read training data) and s3:ListBucket (to validate the bucket and resolve prefixes) on the S3 bucket. The ListBucket permission is often overlooked because it is needed for the initial bucket verification step, even when the full object path is provided. In real-world scenarios, this manifests when using cross-account buckets or VPC endpoints, where bucket policies may also need explicit ListBucket grants.
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.
Modeling — This question tests Modeling — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Missing s3:ListBucket permission — The error occurs because the IAM policy grants s3:GetObject permission on the training data objects but lacks s3:ListBucket permission on the bucket itself. SageMaker's CreateTrainingJob API first performs a ListBucket call to verify the bucket exists and to enumerate objects, even if the exact object key is known. Without s3:ListBucket, the ListBucket call fails, resulting in an access denied error.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 data scientist is setting up a SageMaker training job and has attached this IAM policy to the execution role. The training job fails with an access denied error when trying to write to the output path 's3://my-bucket/output/model.tar.gz'. What additional permission is needed?
hard
✓ A.s3:ListBucket
B.s3:GetObject for the output path
C.s3:DeleteObject
D.iam:PassRole on the role itself
Why A: The training job fails because SageMaker needs to verify that the output S3 bucket exists before writing to it. The s3:ListBucket permission is required to list the contents of the bucket (or confirm its existence) as part of the write operation. Without this permission, the service cannot validate the bucket, resulting in an access denied error even if s3:PutObject is allowed.
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This MLS-C01 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 MLS-C01 exam.
Question Discussion
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