AZ-900 Describe Azure architecture and services Practice Question
A company runs a production web application on Azure App Service. The development team is working on a new version of the application and wants to deploy it to a staging environment to perform validation tests. After testing, they need to gradually shift a percentage of live user traffic to the new version while monitoring for issues. If any problems occur, they must be able to instantly send all traffic back to the original version with zero downtime. Which Azure App Service feature should the team use to achieve this?
⚠ Common exam trap
It's easy for candidates to confuse deployment slots with external load-balancing services like Traffic Manager or Application Gateway, thinking they can achieve the same gradual traffic shifting and instant rollback, but those services operate at different layers and cannot perform a zero-downtime swap within a single App Service instance.
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
✓
Deployment slots
Deployment slots are the correct choice because Azure App Service supports deploying different versions of an application to separate slots (e.g., staging) and then swapping them into production. The swap operation allows you to gradually shift traffic using slot auto-swap or manual swap with traffic routing, and if issues arise, you can instantly swap back to the original slot with zero downtime, as the swap preserves the warm-up state of the target slot.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Deployment slots
Why this is correct
Deployment slots are live environments within App Service that support staged deployment, traffic shifting via slot swapping or slot-specific routing, and instant rollback by swapping back. This feature is purpose-built for zero-downtime deployment and testing.
- ✗
Azure Traffic Manager
Why it's wrong here
Azure Traffic Manager is a DNS-based traffic load balancer that distributes traffic across regional endpoints. While it can route a percentage of traffic to different endpoints, it does not provide staging environments or slot swapping for App Service. It also introduces DNS propagation delays, which makes instant rollback difficult.
- ✗
Azure Application Gateway
Why it's wrong here
Azure Application Gateway is a Layer 7 load balancer and web application firewall. It can route traffic based on URL paths or other criteria, but it does not offer staging environments or the ability to swap application versions with zero downtime. Managing version rollback would require manual reconfiguration.
When this WOULD be correct
A company needs to route HTTP traffic to a web app based on URL path or host headers, and also requires a web application firewall (WAF) to protect against common web vulnerabilities. Azure Application Gateway would be the correct choice for this scenario.
- ✗
Azure Front Door
Why it's wrong here
Azure Front Door is a global HTTP(S) load balancer with traffic acceleration and traffic splitting capabilities. It can shift a percentage of traffic to different backends, but it does not provide the staging environments or the simple swap mechanism that deployment slots offer. It also requires external management of backend swapping.
When this WOULD be correct
A company needs to route traffic across multiple Azure regions for global web application acceleration, SSL offloading, and path-based routing with instant failover. Azure Front Door would be correct for global load balancing and performance optimization.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Deployment slotsCorrect answer▾
Why this is correct
Deployment slots are live environments within App Service that support staged deployment, traffic shifting via slot swapping or slot-specific routing, and instant rollback by swapping back. This feature is purpose-built for zero-downtime deployment and testing.
✗Azure Application GatewayWrong answer — click to see why▾
Why this is wrong here
Azure Application Gateway is a layer 7 load balancer and web application firewall, but it does not provide the ability to gradually shift traffic between app versions or instantly roll back with zero downtime within a single App Service. Deployment slots are the correct feature for staging and traffic shifting.
★ When this WOULD be the correct answer
A company needs to route HTTP traffic to a web app based on URL path or host headers, and also requires a web application firewall (WAF) to protect against common web vulnerabilities. Azure Application Gateway would be the correct choice for this scenario.
Why candidates choose this
Candidates may confuse Application Gateway's traffic routing and WAF capabilities with the staging and traffic shifting features of deployment slots, or think that any load balancing feature can handle gradual rollouts.
✗Azure Front DoorWrong answer — click to see why▾
Why this is wrong here
Azure Front Door is a global load balancer and application delivery suite, but it does not natively support the staging environment with instant traffic shifting and zero-downtime rollback within a single App Service; deployment slots are designed for that.
★ When this WOULD be the correct answer
A company needs to route traffic across multiple Azure regions for global web application acceleration, SSL offloading, and path-based routing with instant failover. Azure Front Door would be correct for global load balancing and performance optimization.
Why candidates choose this
Candidates may confuse Front Door's traffic routing and staging capabilities with deployment slots, or think its 'swap' feature (via backend pools) can replace slot swapping, but Front Door lacks the integrated staging environment and instant rollback of slots.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
Feature
A feature is a distinct unit of functionality that delivers value to the user, often managed and tracked throughout the software development lifecycle.
Key term
Environment
An environment is a dedicated set of computing resources, configurations, and services used to develop, test, or host software applications in a controlled and repeatable way.
About these practice questions
Courseiva writes every AZ-900 question from scratch — 981 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 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-900 exam.