- 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.
Quick Answer
The correct answer is that the CodeBuild project is configured to run in a VPC without a NAT gateway, and the build image is pulled from a public registry. This is because when CodeBuild is attached to a VPC, it loses its default internet access; to pull a Docker image from a public registry like Docker Hub or Amazon ECR Public, the VPC must have a route to the internet, which requires either a NAT gateway in a private subnet or an internet gateway in a public subnet. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how VPC networking constraints affect CodeBuild’s ability to fetch external resources—a common trap is assuming the error stems from insufficient build resources or misconfigured pipeline stages. Remember the key insight: a VPC without a NAT gateway creates a dead end for public image pulls, so always check the VPC configuration first. Memory tip: “No NAT, no pull—your build container’s stuck at the gate.”
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.
Option C is correct because CodeBuild builds run in a VPC that must have a route to pull Docker images from public registries; if the VPC does not have a NAT gateway or internet gateway, the build container cannot pull the base image. Option A is wrong because CodePipeline does not require CodeBuild to be in the same region. Option B is wrong because the error is about pulling the image, not insufficient resources. Option D is wrong because S3 policy does not affect image pulling.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
SDLC Automation — This question tests SDLC Automation — Static NAT maps one inside address to one outside address..
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. — Option C is correct because CodeBuild builds run in a VPC that must have a route to pull Docker images from public registries; if the VPC does not have a NAT gateway or internet gateway, the build container cannot pull the base image. Option A is wrong because CodePipeline does not require CodeBuild to be in the same region. Option B is wrong because the error is about pulling the image, not insufficient resources. Option D is wrong because S3 policy does not affect image pulling.
What should I do if I get this DOP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
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Same concept, more angles
1 more ways this is tested on DOP-C02
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. Your organization uses AWS CodePipeline to orchestrate a multi-stage pipeline for a Java application. The pipeline has a source stage (Amazon S3), a build stage (CodeBuild), and a deploy stage (CodeDeploy to EC2). Recently, the build stage started failing with the error 'BUILD_CONTAINER_UNABLE_TO_PULL_IMAGE'. The build project uses a managed image for Java. You checked the CodeBuild project settings and confirmed that the image is correct. No changes were made to the build project. What is the most likely cause?
medium- A.The S3 bucket policy has been changed to deny access.
- B.The build project's environment variables are incorrectly configured.
- ✓ C.The Docker image specified in the build project is no longer available or the registry is unreachable.
- D.The buildspec.yml file contains invalid syntax.
Why C: Option C is correct because the managed image may have been updated and the pull failed due to network issues. Option A is wrong because the source is S3, not CodeCommit. Option B is wrong because the buildspec is not the cause. Option D is wrong because the environment variables are not related.
Last reviewed: Jun 20, 2026
This DOP-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 DOP-C02 exam.
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