The answer is the SageMaker execution role lacks the necessary permissions to access the S3 bucket. This is correct because SageMaker training jobs assume an IAM execution role to perform actions; even when a cross-account bucket policy grants access to the SageMaker service, the execution role itself must be explicitly listed as a principal in that bucket policy or have its own S3 permissions that the bucket policy allows. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your understanding of how IAM roles and resource-based policies interact across accounts—a common trap is assuming a bucket policy alone is sufficient, but the execution role must be the trusted entity. Remember the memory tip: "Role first, bucket second"—the execution role must be authorized by the bucket policy before SageMaker can access the data.
MLS-C01 Practice Question: Machine Learning Implementation and Operations
This MLS-C01 practice question tests your understanding of machine learning implementation and operations. 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 using Amazon SageMaker to train a model on data stored in S3. The training job needs to access data from an S3 bucket in a different AWS account. The data owner has granted cross-account access via a bucket policy. However, the training job fails with an AccessDenied error. 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
✓
The SageMaker execution role does not have the necessary permissions to access the S3 bucket.
Option A is correct because SageMaker training jobs use an execution role; that role must be granted cross-account access via the bucket policy. Option B is wrong because S3 does not require VPC endpoints for cross-account access. Option C is wrong because the data does not need to be public. Option D is wrong because KMS encryption is not the issue unless the bucket policy denies.
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 data is encrypted with SSE-KMS and the SageMaker role lacks KMS permissions.
Why it's wrong here
KMS permissions would cause a different error message.
✓
The SageMaker execution role does not have the necessary permissions to access the S3 bucket.
Why this is correct
The IAM role used by SageMaker must be allowed in the bucket policy.
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 S3 bucket is not configured with public access.
Why it's wrong here
Cross-account access does not require public access.
✗
The S3 bucket is in a different region and requires a VPC endpoint.
Why it's wrong here
Cross-region access works without VPC endpoints.
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 MLS-C01 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.
Machine Learning Implementation and Operations — This question tests Machine Learning Implementation and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The SageMaker execution role does not have the necessary permissions to access the S3 bucket. — Option A is correct because SageMaker training jobs use an execution role; that role must be granted cross-account access via the bucket policy. Option B is wrong because S3 does not require VPC endpoints for cross-account access. Option C is wrong because the data does not need to be public. Option D is wrong because KMS encryption is not the issue unless the bucket policy denies.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 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.
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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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 using Amazon SageMaker to train a model. The training data is stored in an S3 bucket in a different AWS account. Which IAM policy configuration is required to allow SageMaker to access the data?
easy
A.Add a bucket policy that allows s3:GetObject for the SageMaker execution role's ARN.
✓ B.Add a bucket policy allowing access from the SageMaker execution role ARN, and ensure the SageMaker execution role has an IAM policy allowing s3:GetObject on the bucket.
C.Create an IAM user in the data owner's account and use its credentials in SageMaker.
D.Use the data owner's IAM role as the SageMaker execution role.
Why B: Option B is correct because cross-account access requires the SageMaker execution role to have an IAM policy allowing access to the S3 bucket, and the S3 bucket policy must grant access to that role. Option A is wrong because SageMaker cannot assume a role in another account without proper trust policy. Option C is wrong because the data owner's role cannot be used directly. Option D is wrong because SageMaker does not use the data owner's IAM user credentials.
Last reviewed: Jun 20, 2026
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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.
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