The answer is that the output bucket is not listed in the Resource of the IAM policy. This is the most likely cause because the Glue job’s IAM service role explicitly restricts s3:PutObject to only ‘example-bucket’, but the job is attempting to write to a different S3 bucket, resulting in an Access Denied error. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of least-privilege IAM policies and how S3 resource ARNs must exactly match the buckets your Glue job accesses. A common trap is assuming the job role has blanket S3 permissions or confusing the role’s Glue actions with S3 actions—remember, the policy must list every bucket used for read and write operations. Memory tip: “If it’s not in the Resource, it’s a dead course—always check the ARN for the bucket you’re writing to.”
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. 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 engineer is troubleshooting an AWS Glue job that reads from an S3 bucket and writes to another S3 bucket. The job fails with an 'Access Denied' error when trying to write to the output bucket. The IAM policy attached to the Glue service role is shown. What is the MOST likely cause of the failure?
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 output bucket is not listed in the Resource of the IAM policy
The policy only allows s3:GetObject and s3:PutObject on 'example-bucket', but the job is writing to a different bucket. The Glue job needs permissions on the output bucket as well. Option A is wrong because the job role has permissions for Glue actions. Option B is wrong because S3 permissions are for a specific bucket. Option D is wrong because the job role is separate from the user role.
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 user who runs the job does not have S3 permissions
Why it's wrong here
The job runs under the service role, not the user.
✗
The Glue job role does not have permissions to start a job run
Why it's wrong here
The policy allows glue:StartJobRun.
✓
The output bucket is not listed in the Resource of the IAM policy
Why this is correct
The policy only allows PutObject on example-bucket, not the output bucket.
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 policy denies access to the Glue service
Why it's wrong here
There is no indication of bucket policy; the IAM policy is insufficient.
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.
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 output bucket is not listed in the Resource of the IAM policy — The policy only allows s3:GetObject and s3:PutObject on 'example-bucket', but the job is writing to a different bucket. The Glue job needs permissions on the output bucket as well. Option A is wrong because the job role has permissions for Glue actions. Option B is wrong because S3 permissions are for a specific bucket. Option D is wrong because the job role is separate from the user role.
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.
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Question Discussion
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