AZ-400 Practice Question: Design and implement build and release pipelines
Your Azure DevOps pipeline deploys a web app to Azure App Service using a YAML pipeline. The deployment fails intermittently with the error 'Conflict' when updating deployment slots. What is the most likely cause?
⚠ Common exam trap
Candidates often confuse a 'Conflict' error with authentication or configuration issues, but Azure specifically returns HTTP 409 only when a resource-level lock prevents the operation, not for credential or naming problems.
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
✓
Another deployment or swap operation is already in progress on the slot.
The 'Conflict' error during an Azure App Service deployment slot update indicates that the slot is currently locked by another operation, such as an ongoing deployment or a swap. Azure App Service enforces mutual exclusion on slot operations to prevent race conditions, so if a previous deployment or swap has not completed, the new request is rejected with HTTP 409 Conflict.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Another deployment or swap operation is already in progress on the slot.
Why this is correct
Azure App Service serializes deployment and swap operations per slot, returning an HTTP 409 Conflict when a second operation is attempted concurrently. This error indicates that a previous deployment or swap has not yet completed, so you must wait for it to finish or cancel it before retrying.
- ✗
The service connection is using expired credentials.
Why it's wrong here
Expired credentials in a service connection cause authentication failures (HTTP 401) or authorization errors (HTTP 403), not a conflict error. This issue is unrelated to concurrent operation serialization and would manifest long before any slot-level operation begins.
- ✗
The slot name is misspelled in the pipeline configuration.
Why it's wrong here
A misspelled slot name in a pipeline configuration produces a 'not found' error (HTTP 404) because Azure App Service cannot locate the specified slot. It does not trigger a conflict error, which requires an existing slot already performing an operation.
- ✗
The web app is locked by a file handle from a previous deployment.
Why it's wrong here
A file handle lock is an operating-system-level condition that prevents specific files from being overwritten or deleted, producing errors such as 'access denied' or 'being used by another process' during the physical file copy phase. It does not generate an HTTP 409 Conflict, which is an orchestration-level response from Azure's control plane. The 409 arises only when the App Service resource manager detects that another deployment or swap operation is already running on the same slot, regardless of any file-level locks. In short, file handles affect the filesystem, not the slot's operation state machine.
Go deeper
Related to this question
Learn chapter
Introduction to DevOps and Azure DevOps
Key term
Pipeline
A pipeline is an automated series of steps that takes code from development to production, ensuring quality and speed.
Key term
Azure DevOps
Azure DevOps is a Microsoft service that provides development tools for planning, building, testing, and deploying software applications using automated pipelines and collaboration features.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.