Why an App Service Deployment Succeeds but the App Never Starts
Network Topology
You run the Azure CLI command shown in the exhibit as part of a release pipeline to deploy a ZIP package to an Azure App Service. The deployment succeeds, but the app does not start. What is the most likely cause?
Quick Answer
A ZIP-deploy that succeeds but never starts the app almost always means the App Service's startup command was never configured — az webapp deploy pushes the code but doesn't set how to run it, so the platform falls back to a generic handler that doesn't know how to launch something like a custom Node or Python entry point. Setting --startup-file explicitly (via az webapp config set or the portal) fixes it.
⚠ Common exam trap
It's easy for candidates to assume a successful deployment (no CLI errors) guarantees the app will run, but Azure App Service separates the deployment of artifacts from the runtime configuration, so a missing startup command is a common silent failure.
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 app's startup command is not configured
The Azure CLI command `az webapp deploy` deploys the ZIP package to the App Service, but it does not configure the startup command. If the application (e.g., a Node.js or Python app) requires a specific startup file or script (like `npm start` or `gunicorn`), the App Service will fail to start because it defaults to a generic handler. The startup command must be set via the `--startup-file` parameter in `az webapp config set` or in the Azure portal.
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 app's startup command is not configured
Why this is correct
ZIP deploy via Azure CLI unpacks files but App Service runs no build automation, so without an explicit startup command the container has no entry point and the app never launches. The deployment succeeds because files land correctly; the failure is purely at process start.
- ✗
The resource group name is incorrect
Why it's wrong here
A wrong resource group name would make the deployment fail outright, yet the stem states it succeeded, so this cannot explain the app failing to start. It tempts because resource group mistakes are a common deployment error, but here the ZIP deployed and the startup command is the actual problem.
- ✗
The runtime stack is not specified in the command
Why it's wrong here
The runtime stack is configured on the App Service plan or web app, not passed in the deployment command, so omitting it does not stop the app starting. It tempts because stack mismatches do cause startup failures, but the deployment command's startup behaviour is governed by the app's startup command setting.
- ✗
The deployment slot is not specified
Why it's wrong here
Omitting a deployment slot deploys to the production slot, which still runs the app; slot selection does not cause a startup failure. It tempts because slots are used for staged releases, but the stem's symptom points to the startup command, not to which slot received the ZIP.
Go deeper
Related to this question
Learn chapter
Managing Build Quality and Package Dependencies
Key term
Release pipeline
A Release pipeline is an automated sequence of steps that takes software from code commit to production deployment, ensuring quality and consistency.
Key term
Pipeline
A pipeline is an automated series of steps that takes code from development to production, ensuring quality and speed.
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Same concept, more angles
1 more way this is tested on AZ-400
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. You are creating a release pipeline that deploys to Azure App Service. You want to ensure that the deployment uses the 'Run from package' feature for faster deployments and reduced downtime. Which deployment method should you select in the 'Azure App Service deploy' task?
easy- A.Web Deploy
- B.Container
- ✓ C.RunFromPackage
- D.Zip Deploy
Why C: The 'Run from package' feature deploys your app as a zip package directly to Azure App Service, bypassing the file copy and compilation steps of traditional methods. This reduces deployment time and downtime because the app runs from the package without extracting it to the wwwroot folder. Selecting 'RunFromPackage' in the Azure App Service deploy task enables this behavior by setting the WEBSITE_RUN_FROM_PACKAGE app setting to 1.
JA
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.