Resolving Access Denied Error for S3 Source in AWS CodeBuild by Adding s3:GetObject to Service Role
This DOP-C02 practice question tests your understanding of sdlc automation. 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.
Network Topology
Refer to the exhibit. A developer runs the AWS CLI command to start a build in AWS CodeBuild. The build project 'my-project' uses an S3 bucket as the source. What is the MOST likely cause of the error?
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.
Network Topology
A
The CodeBuild service role does not have s3:GetObject permission on the source bucket.
CodeBuild assumes a service role to access sources; that role needs S3 read permission.
B
The S3 bucket name is misspelled in the build project configuration.
Why wrong: The error does not indicate a misspelling; it says insufficient permissions.
C
The developer's IAM user does not have s3:GetObject permission.
Why wrong: The error mentions the role, not the user.
D
The S3 bucket is in a different region than the CodeBuild project.
Why wrong: Cross-region access is possible with proper permissions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The CodeBuild service role does not have s3:GetObject permission on the source bucket.
The error occurs because CodeBuild needs to download the source code from the S3 bucket during the build. The CodeBuild service role, not the developer's IAM user, makes the s3:GetObject API call to retrieve the source object. Without this permission on the service role, the build fails with 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 CodeBuild service role does not have s3:GetObject permission on the source bucket.
Why this is correct
CodeBuild assumes a service role to access sources; that role needs S3 read permission.
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 name is misspelled in the build project configuration.
Why it's wrong here
The error does not indicate a misspelling; it says insufficient permissions.
✗
The developer's IAM user does not have s3:GetObject permission.
Why it's wrong here
The error mentions the role, not the user.
✗
The S3 bucket is in a different region than the CodeBuild project.
Why it's wrong here
Cross-region access is possible with proper permissions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the developer's IAM permissions with the CodeBuild service role's permissions, assuming the developer's credentials are used for all actions, when in fact CodeBuild uses its own role for resource access.
Detailed technical explanation
How to think about this question
Under the hood, CodeBuild assumes the service role (specified in the project's serviceRole ARN) to perform actions like downloading source from S3. The STS AssumeRole API is used to obtain temporary credentials for that role. If the role lacks s3:GetObject on the source bucket's ARN (e.g., arn:aws:s3:::bucket-name/object-key), the S3 API returns an AccessDenied (HTTP 403) error. This is a common misconfiguration when developers assume their own IAM permissions are sufficient.
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.
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The CodeBuild service role does not have s3:GetObject permission on the source bucket. — The error occurs because CodeBuild needs to download the source code from the S3 bucket during the build. The CodeBuild service role, not the developer's IAM user, makes the s3:GetObject API call to retrieve the source object. Without this permission on the service role, the build fails with an access denied error.
What should I do if I get this DOP-C02 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.
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Question Discussion
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