AZ-400 Design and implement source control Practice Question
This AZ-400 practice question tests your understanding of design and implement source control. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You are a DevOps engineer for a company developing a mobile application. The source code is stored in Azure Repos (Git). The team uses trunk-based development with short-lived feature branches. Recently, developers have reported that their feature branch builds are taking over 30 minutes, whereas the main branch builds complete in under 10 minutes. The pipeline is defined in a YAML file and includes steps to restore NuGet packages, compile, run unit tests, and perform code analysis. The pipeline also publishes build artifacts. The main branch has a branch policy that requires a successful build before merging. The feature branches do not have branch policies. All builds run on Microsoft-hosted agents. Upon investigation, you notice that the feature branch builds are restoring all NuGet packages from scratch each time, while main branch builds use cached packages. Additionally, the code analysis tool is scanning the entire codebase, not just the changed files. You need to reduce the feature branch build time to under 15 minutes without compromising code quality. Which course of action should you take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable pipeline caching for NuGet packages and configure the code analysis step to scan only changed files using path filters.
Option B is correct because it directly addresses the two root causes of the slow feature branch builds: uncached NuGet package restores and full-codebase code analysis. Enabling pipeline caching (using the Cache@2 task) stores the NuGet packages folder (typically ~/.nuget/packages) and restores it on subsequent runs, eliminating redundant downloads. Configuring the code analysis step with path filters (e.g., using the 'changedFiles' condition or a custom script) ensures only modified files are scanned, drastically reducing analysis time without sacrificing quality.
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.
✗
Configure a self-hosted agent with pre-installed dependencies and a larger disk for faster I/O.
Why it's wrong here
Self-hosted agents require maintenance and may not solve the caching or analysis scope issues.
✓
Enable pipeline caching for NuGet packages and configure the code analysis step to scan only changed files using path filters.
Why this is correct
Caching reduces restore time, and scanning only changed files reduces analysis time.
Related concept
Read the scenario before looking for a memorised answer.
✗
Remove the code analysis step from feature branch builds and only run it on main branch builds.
Why it's wrong here
This compromises code quality on feature branches.
✗
Increase the agent VM size to a more powerful SKU for feature branch builds.
Why it's wrong here
This increases cost and may not address the root causes of cache misses and full code analysis.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume hardware upgrades (larger agents or self-hosted machines) are the solution, when the real issue is inefficient pipeline logic—specifically, missing caching and incremental scanning—which are software-level optimizations that directly target the root causes.
Detailed technical explanation
How to think about this question
Pipeline caching in Azure DevOps uses a cache key (typically based on the lock file or project file hash) to store and retrieve the NuGet packages folder from a shared storage blob. The code analysis tool (e.g., Roslyn analyzers or SonarQube) can be configured with a 'changed files' filter using the `git diff` command or the `changedFiles` predefined variable in YAML, which compares the current commit to the merge base with the target branch. In trunk-based development with short-lived feature branches, these optimizations are critical because feature branches often have few changes but trigger full builds, leading to wasted time and compute.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-400 question in full detail.
Design and implement source control — This question tests Design and implement source control — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable pipeline caching for NuGet packages and configure the code analysis step to scan only changed files using path filters. — Option B is correct because it directly addresses the two root causes of the slow feature branch builds: uncached NuGet package restores and full-codebase code analysis. Enabling pipeline caching (using the Cache@2 task) stores the NuGet packages folder (typically ~/.nuget/packages) and restores it on subsequent runs, eliminating redundant downloads. Configuring the code analysis step with path filters (e.g., using the 'changedFiles' condition or a custom script) ensures only modified files are scanned, drastically reducing analysis time without sacrificing quality.
What should I do if I get this AZ-400 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This AZ-400 practice question is part of Courseiva's free Microsoft 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 AZ-400 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.