- A
The CodeBuild project is in a different AWS Region than the CodePipeline pipeline.
Why wrong: Cross-region pipelines are supported; region mismatch does not cause this specific error.
- B
The CodeBuild project is configured to run in a VPC without a NAT gateway, and the build image is pulled from a public registry.
Without a NAT gateway, the build container cannot access the public internet to pull the image.
- C
The S3 bucket where the source code is stored has a bucket policy denying access to the CodeBuild service role.
Why wrong: If the source were inaccessible, the error would occur earlier; the error is specific to pulling the build image.
- D
The CodeBuild project does not have enough memory or vCPU allocated.
Why wrong: Resource allocation affects build performance but not the ability to pull the base image.
DOP-C02 SDLC Automation Practice Question
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.
A development team is implementing a CI/CD pipeline using AWS CodePipeline. The pipeline has a Source stage connected to an Amazon S3 bucket, a Build stage using AWS CodeBuild, and a Deploy stage that deploys to an Amazon ECS cluster. The team notices that the pipeline fails intermittently during the Build stage with a 'BUILD_CONTAINER_UNABLE_TO_PULL_IMAGE' 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 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 CodeBuild project is configured to run in a VPC without a NAT gateway, and the build image is pulled from a public registry.
The 'BUILD_CONTAINER_UNABLE_TO_PULL_IMAGE' error in AWS CodeBuild indicates that the build environment cannot pull the specified Docker image from its registry. When a CodeBuild project is configured to run in a VPC without a NAT gateway, it lacks outbound internet access, which is required to pull images from public registries like Docker Hub or Amazon ECR public. This is the most likely cause because the error is intermittent (e.g., if the image is cached locally sometimes) and directly relates to network connectivity.
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 project is in a different AWS Region than the CodePipeline pipeline.
Why it's wrong here
Cross-region pipelines are supported; region mismatch does not cause this specific error.
- ✓
The CodeBuild project is configured to run in a VPC without a NAT gateway, and the build image is pulled from a public registry.
- ✗
The S3 bucket where the source code is stored has a bucket policy denying access to the CodeBuild service role.
Why it's wrong here
If the source were inaccessible, the error would occur earlier; the error is specific to pulling the build image.
- ✗
The CodeBuild project does not have enough memory or vCPU allocated.
Why it's wrong here
Resource allocation affects build performance but not the ability to pull the base image.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse VPC networking errors with permission or resource errors, overlooking that CodeBuild in a VPC without a NAT gateway blocks outbound traffic to public registries, which is a subtle but critical detail for the 'BUILD_CONTAINER_UNABLE_TO_PULL_IMAGE' error.
Detailed technical explanation
How to think about this question
CodeBuild by default uses an AWS-managed network with outbound internet access, but when a VPC is configured, the build container runs within that VPC and inherits its routing rules. Without a NAT gateway or internet gateway, the build environment cannot reach public registries (e.g., Docker Hub on port 443) to pull images, causing the error. This is a common issue in private subnets where developers forget to add a NAT gateway or VPC endpoints for Amazon ECR (com.amazonaws.region.ecr.dkr and com.amazonaws.region.ecr.api) to allow image pulls from private registries.
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.
Visual reference
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.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
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 project is configured to run in a VPC without a NAT gateway, and the build image is pulled from a public registry. — The 'BUILD_CONTAINER_UNABLE_TO_PULL_IMAGE' error in AWS CodeBuild indicates that the build environment cannot pull the specified Docker image from its registry. When a CodeBuild project is configured to run in a VPC without a NAT gateway, it lacks outbound internet access, which is required to pull images from public registries like Docker Hub or Amazon ECR public. This is the most likely cause because the error is intermittent (e.g., if the image is cached locally sometimes) and directly relates to network connectivity.
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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Last reviewed: Jul 4, 2026
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