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Identity and Access ManagementhardMultiple ChoiceObjective-mapped

SCS-C02 Bucket Policy Principal Practice Question

This SCS-C02 practice question tests your understanding of identity and access management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: bucket Policy Principal. 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 developer is trying to upload an object to an S3 bucket named 'my-bucket' using the AWS CLI. The developer has an IAM user with a policy that includes 's3:PutObject' for 'arn:aws:s3:::my-bucket/*'. However, the upload fails with an 'Access Denied' error. The bucket policy is set to allow all principals from the same AWS account to perform 's3:PutObject'. What is the most likely cause of this 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 choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

The bucket policy denies access because the principal is not explicitly listed.

The IAM user has s3:PutObject permission on the bucket's objects (/*), so option A is incorrect. Option C is incorrect because s3:PutObject is always applied to the object resource (e.g., bucket-name/*); no upload operation requires the same permission on the bucket itself. Option D is incorrect because a region mismatch would result in a NoSuchBucket error, not Access Denied. Option B is correct because the bucket policy, though intended to allow all principals from the same AWS account, typically specifies the AWS account root principal (e.g., "arn:aws:iam::account-id:root"). This principal only grants access to the root user, not to IAM users. Since the IAM user is not an explicitly listed principal, the request is implicitly denied, resulting in the Access Denied error.

Key principle: Bucket Policy Principal

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 IAM user is not authorized to perform 's3:PutObject' on the bucket 'my-bucket'.

    Why it's wrong here

    Incorrect. The IAM user policy does grant s3:PutObject on the object ARN, so this option is not the cause.

  • The bucket policy denies access because the principal is not explicitly listed.

    Why this is correct

    Correct. The bucket policy likely uses the root principal, which does not cover the IAM user, resulting in an implicit deny.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    Bucket Policy Principal

  • The IAM policy grants 's3:PutObject' only on objects (/*), but the request may also require 's3:PutObject' on the bucket itself for some operations.

    Why it's wrong here

    Incorrect. s3:PutObject does not require permission on the bucket ARN; the action is always on objects. The error stems from the bucket policy not listing the IAM user.

  • The bucket 'my-bucket' does not exist in the same region as the CLI request.

    Why it's wrong here

    Incorrect. A region mismatch would yield a NoSuchBucket or redirect error, not an Access Denied.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap is that candidates assume that specifying the AWS account root principal in a bucket policy allows all IAM users in the account, but it only permits the root user. Additionally, learners may overlook that both the IAM policy and bucket policy must explicitly allow the requester; if the bucket policy does not include the IAM user as a principal, access is denied.

Detailed technical explanation

How to think about this question

Under the hood, the AWS CLI often uses multipart uploads for objects larger than 5 MB, which requires the 's3:PutObject' permission on the bucket resource (arn:aws:s3:::my-bucket) to initiate the upload, in addition to the object-level permission. This is a subtle distinction between bucket-level and object-level ARNs; the IAM policy must explicitly grant the action on both ARNs for multipart uploads to succeed. In real-world scenarios, this trap catches developers who assume object-level permissions are sufficient for all upload operations.

KKey Concepts to Remember

  • Bucket Policy Principal
  • IAM vs Bucket Policy Evaluation
  • s3:PutObject Resource ARN

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

Bucket Policy Principal

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 ClassMin DurationRetrievalUse Case
S3 StandardNoneImmediateFrequently accessed data
S3 Standard-IA30 daysImmediateInfrequent access, rapid retrieval
S3 One Zone-IA30 daysImmediateNon-critical infrequent data
S3 Intelligent-TieringNoneImmediate–hoursUnknown or changing access patterns
S3 Glacier Instant90 daysMillisecondsArchive with instant retrieval
S3 Glacier Flexible90 daysMinutes–hoursArchive, flexible retrieval
S3 Glacier Deep Archive180 daysHoursLong-term compliance archive

What to study next

Got this wrong? Here's your next step.

Review bucket Policy Principal, then practise related SCS-C02 questions on the same topic to reinforce the concept.

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FAQ

Questions learners often ask

What does this SCS-C02 question test?

Identity and Access Management — This question tests Identity and Access Management — Bucket Policy Principal.

What is the correct answer to this question?

The correct answer is: The bucket policy denies access because the principal is not explicitly listed. — The IAM user has s3:PutObject permission on the bucket's objects (/*), so option A is incorrect. Option C is incorrect because s3:PutObject is always applied to the object resource (e.g., bucket-name/*); no upload operation requires the same permission on the bucket itself. Option D is incorrect because a region mismatch would result in a NoSuchBucket error, not Access Denied. Option B is correct because the bucket policy, though intended to allow all principals from the same AWS account, typically specifies the AWS account root principal (e.g., "arn:aws:iam::account-id:root"). This principal only grants access to the root user, not to IAM users. Since the IAM user is not an explicitly listed principal, the request is implicitly denied, resulting in the Access Denied error.

What should I do if I get this SCS-C02 question wrong?

Review bucket Policy Principal, then practise related SCS-C02 questions on the same topic to reinforce the concept.

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?

Bucket Policy Principal

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Last reviewed: Jun 11, 2026

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This SCS-C02 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 SCS-C02 exam.