AZ-400 Design and implement source control — Timed 15 Questions

Question 1

Your team manages a large monorepo in Azure Repos containing multiple microservices. The repository has grown to over 10,000 files and 500 MB. Developers report that cloning and fetching operations are slow, often taking more than 10 minutes. Additionally, the CI pipeline triggers on every push to any branch, causing long queue times. You need to improve the developer experience and CI efficiency without splitting the repository. What should you do?

15 minute time limit — choose an answer to begin.

Accepted Answer

Use Git sparse checkout to clone only the folders needed for each microservice, and configure path-based CI triggers to run only when files in specific directories change.. Git sparse checkout allows developers to limit the working tree to specific directories, reducing local disk usage and checkout time. However, a standard sparse checkout alone does not reduce the amount of data downloaded during a full clone—this requires combining it with shallow or partial clone options. In Azure Pipelines, path-based CI triggers ensure pipelines run only when files in relevant directories change, reducing unnecessary builds and queue times. This approach improves both developer experience and CI efficiency without splitting the monorepo.

Answer

Configure shallow clone (depth=1) for all operations and disable CI triggers on feature branches.

Answer

Break the monorepo into multiple smaller repositories and use Git submodules to manage dependencies.

Answer

Implement Git Virtual File System (GVFS) for the repository and use CI triggers only on the main branch.

Question 2

Refer to the exhibit. A developer attempts to push a commit directly to the main branch of FabrikamWeb repository but receives a push rejection. What is the most likely reason?

Accepted Answer

The developer does not have permission to push to the main branch due to branch policies requiring pull requests.. The developer's direct push to main was rejected because the main branch has an active branch policy that requires all changes to be introduced via pull requests. In Azure DevOps, any branch policy (such as 'Require a minimum number of reviewers' or 'Require pull request comments resolution') blocks direct pushes to that branch, even if the user has 'Contribute' permission. The exhibit likely shows branch policies applied to the main branch, which prevents direct pushes. An incorrect remote URL would typically result in a 'repository not found' error, and a non-existent branch would produce a different error. Therefore, the most likely reason is that branch policies on main require pull requests.

Answer

The developer tried to push to the wrong remote URL.

Answer

The FabrikamWeb repository has a minimum number of reviewers policy set to 1, which blocks direct pushes.

Answer

The main branch does not exist in the FabrikamWeb repository.

Question 3

Refer to the exhibit. A developer sees this error when running a YAML pipeline in Azure DevOps. What is the most likely cause?

Accepted Answer

The Azure DevOps organization has no available parallel jobs.. The pipeline error requires the exhibit to identify the exact message. Without it, none of the options can be confirmed as the most likely cause. The question should be revised or removed.

Answer

The pipeline agent pool is misconfigured.

Answer

The pipeline YAML file has a syntax error.

Answer

The Azure subscription is not linked to the Azure DevOps organization.

Question 4

A team uses a monorepo with multiple projects in one Git repository. They want to enforce that each commit message must reference a work item from Azure Boards. Which branch policy should they configure?

Accepted Answer

Use a build validation policy to check commit messages. The 'Require a work item linking policy' in Azure Repos ensures each pull request is linked to a work item, but it does not validate that each commit message contains a reference. To enforce that commit messages themselves reference an Azure Boards work item, a build validation policy can run a script to verify the commit message format. Therefore, option D is the correct choice.

Answer

Automatically include work items in pull request descriptions

Answer

Require a work item linking policy in branch policies

Answer

Configure a minimum number of reviewers policy

Question 5

An organization has multiple Git repositories. Developers often forget to update the repository README file after making changes. What is the most effective way to ensure the README is always up-to-date?

Accepted Answer

Add a task in the CI pipeline that checks if the README was modified. Adding a task in the CI pipeline that checks whether the README was modified directly enforces that developers include README updates in the same pull request that contains code changes. This ensures the README stays current with the codebase. In Azure Repos, CI pipelines can easily validate file changes using scripts or tasks. Option C (repository template) only ensures a README exists for new repositories but does not enforce updates after initial creation, so it does not address the core issue of keeping the README up-to-date over time.

Answer

Apply a label to PRs that touch certain files and require review

Answer

Use a repository template with a mandatory README file structure

Answer

Require a pull request comment that confirms README update

Question 6

A development team uses a forking workflow in Azure Repos. They want to ensure that only specific users can create forks of the main repository. How can they achieve this?

Accepted Answer

Remove the 'Create Fork' permission from all users except the required group. In Azure Repos, the ability to create forks is controlled by the 'Create Fork' permission, which is a repository-level permission, not a branch-level setting. By default, all contributors have this permission. To restrict fork creation to only specific users, navigate to the repository settings, go to Security (or Permissions), remove the 'Create Fork' permission from all users and groups, then explicitly grant it only to the desired group or individuals. Therefore, the correct answer is D: remove the 'Create Fork' permission from all users except the required group.

Answer

Use branch security to restrict who can create forks

Answer

Set branch policies on the main branch to prevent forks

Answer

Configure the repository to disable forks globally

Question 7

A team uses Git for source control. They want to automatically squash all commits in a feature branch into a single commit when merging to the main branch. Which merge type should they use?

Accepted Answer

Squash commit. B is correct because the squash commit merge type collapses all commits in a feature branch into a single new commit on the target branch. This satisfies the requirement to automatically squash all commits when merging to main, as it creates a clean, linear history with one combined commit that contains all changes from the feature branch.

Answer

Rebase and fast-forward

Answer

Merge commit (no fast-forward)

Answer

Semi-linear merge

Question 8

A company has a policy that all code changes must be reviewed by at least two people. However, for urgent bug fixes, they want to allow a single reviewer. How should they configure the branch policy?

Accepted Answer

Set minimum number of reviewers to 2, but allow policy override for urgent fixes. Azure Repos branch policies allow you to set a minimum number of reviewers (e.g., 2) and then enable the 'Allow policy override' setting for urgent fixes. This lets authorized users bypass the two-reviewer requirement for critical bug fixes while maintaining the default policy for normal changes.

Answer

Set minimum number of reviewers to 1 and require a separate approval from a manager

Answer

Set minimum number of reviewers to 2 and allow resetting code review votes on new pushes

Answer

Configure a build validation policy that checks number of approvals

Question 9

A team uses Git-LFS to store large binary files. They observe that cloning the repository takes a long time because Git-LFS files are downloaded. How can they improve clone performance?

Accepted Answer

Use the --filter=blob:none option when cloning. The `--filter=blob:none` option performs a partial clone, which omits all blob objects (including Git-LFS pointer files and other large blobs) from the initial download. This significantly reduces clone time by only fetching commit and tree metadata, and then lazily downloading blobs on demand when they are actually accessed. For Git-LFS specifically, this avoids downloading the large binary files stored in LFS until they are needed, improving clone performance.

Answer

Use a shallow clone with depth 1

Answer

Use sparse checkout to limit files in working directory

Answer

Configure git lfs prune to run automatically

Question 10

A developer accidentally committed a sensitive password to a Git repository. The commit has already been pushed to the remote. What is the first step to remediate the situation?

Accepted Answer

Immediately notify the security team and rotate the password. Once a secret is pushed to a remote Git repository, it must be considered compromised because the commit may already be fetched by others, and old commits remain in reflogs and other clones. The first step is to immediately notify the security team and rotate/revoke the password to prevent unauthorized use. Only after the credential is invalidated should you attempt to remove it from Git history (e.g., by amending, rebasing, or using filter-repo) and force push, understanding that history rewriting may not fully eliminate all copies.

Answer

Delete the file from the repository and commit the deletion

Answer

Remove the password from the file, amend the commit, and force push

Answer

Revert the commit that introduced the password

Question 11

A team is migrating from TFVC to Git. They have a large codebase with many branches. What is the recommended approach to preserve the history during migration?

Accepted Answer

Use the git-tfs tool to clone the TFVC repository with changesets. Git-tfs is a specialized bridge tool that converts TFVC changesets into Git commits, preserving the full history, author information, and branch structure during migration. Unlike Git-TF, which is deprecated and lacks support for newer TFVC features, git-tfs handles complex scenarios like merges and shelvesets, making it the recommended approach for preserving history when moving from TFVC to Git.

Answer

Copy the latest version of the code to a new Git repository and start fresh

Answer

Use the Git-TF tool to clone the TFVC repository

Answer

Export TFVC as a Git bundle and import with --no-metadata

Question 12

Which TWO branch policies can be configured in Azure Repos to enforce code quality?

Accepted Answer

Status check. Status check (A) is correct because Azure Repos allows you to require that a status check passes before a pull request can be completed. This enforces code quality by integrating with external or built-in services (e.g., Azure Pipelines, SonarQube) that run automated tests, linting, or security scans. Build validation (C) is correct because it triggers a build pipeline automatically when a pull request is created, ensuring the code compiles and passes defined quality gates before merging.

Answer

Comment requirements

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Work item linking

Answer

Merge strategy

Question 13

Which THREE are benefits of using a monorepo vs multiple repositories?

Accepted Answer

Easier code sharing and refactoring across projects. A monorepo enables easier code sharing and refactoring across projects by allowing all code to reside in a single repository. This eliminates the need for cross-repository package publishing or versioning, as shared libraries can be directly referenced and refactored atomically across all dependent projects within the same commit.

Answer

Reduced risk of configuration drift

Answer

Faster clone times due to smaller repository size

Question 14

Which THREE are valid Git merge strategies available in Azure Repos pull requests?

Accepted Answer

Semi-linear merge. Among the given options, the valid merge strategies are: 'Merge commit (no fast-forward)' (Option B), 'Semi-linear merge' (Option A), and 'Squash merge' (Option D). 'Merge commit (no fast-forward)' preserves the full history of both branches. 'Semi-linear merge' rebases the source branch onto the target before creating a merge commit, ensuring linear history. 'Squash merge' combines all source branch commits into a single commit on the target. Note that Azure Repos also supports 'Rebase and fast-forward' as a valid merge strategy, but it is not among the options. Options C and E are not valid merge strategies in Azure Repos pull requests.

Answer

Fast-forward only

Answer

Rebase only

Question 15

You are a DevOps engineer at a company that develops a cloud-based SaaS application. The application consists of multiple microservices, each stored in its own Git repository within a single Azure DevOps project. The team has grown rapidly, and developers frequently need to make changes that span multiple services. They often complain about the overhead of managing multiple pull requests and coordinating merges across repositories. To improve efficiency, the team lead suggests consolidating all microservices into a single monorepo. However, the lead architect is concerned about the impact on build times, as the CI pipeline currently builds each service independently. You are tasked with designing a source control strategy that reduces cross-repository coordination overhead while maintaining fast, independent builds. You propose using a monorepo with a structure that allows selective building. Which approach should you recommend?

Accepted Answer

Create a single monorepo with a build pipeline that uses path filters to trigger builds only for changed services. Using a single monorepo with path filters in the build pipeline allows you to trigger builds only for the microservices that have changed, reducing cross-repository coordination overhead while maintaining fast, independent builds. Path filters in Azure Pipelines (e.g., `paths` in YAML) enable selective triggering based on file paths, so unchanged services are not rebuilt, preserving CI efficiency.

Answer

Keep separate repositories but create a meta-repo that references them as submodules

Answer

Keep separate repositories but use Git submodules to share code

Answer

Create a single monorepo with all services and a single build pipeline that builds everything