AZ-204 Develop Azure compute solutions Practice Question
You are deploying a new version of an ASP.NET Core web application to Azure App Service. You want to test the new version with a subset of users before making it available to everyone. You also need to be able to switch back instantly if issues are found. Which App Service feature should you use?
⚠ Common exam trap
Candidates often confuse Azure Traffic Manager (DNS-level routing) with deployment slots (App Service–level routing), not realizing that Traffic Manager cannot provide instant rollback or cookie-based traffic splitting 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
✓
Use deployment slots with swapping.
Deployment slots in Azure App Service allow you to deploy a new version of your application to a staging slot, then gradually route a subset of user traffic to it using slot-specific routing rules (e.g., cookie-based affinity). If issues arise, you can instantly revert by swapping the slots back, which requires no redeployment and preserves the previous version's warm instances.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a separate App Service plan and deploy the new version there.
Why it's wrong here
Creating a separate App Service plan means provisioning entirely new compute resources, leading to increased operational costs and management overhead for two distinct environments. This approach lacks integrated traffic routing capabilities for seamless version transitions or instant rollback, requiring manual DNS changes or an external load balancer to direct traffic between the old and new deployments, which complicates blue/green deployments.
- ✗
Use Azure DevOps deployment pipelines with deployment gates.
Why it's wrong here
Azure DevOps deployment pipelines with deployment gates are designed to automate and control the *progression* of a release through various stages, ensuring quality checks and approvals are met before promotion. However, gates do not provide the runtime traffic management features like instant swapping of application versions or dynamic traffic routing between live deployments, which are crucial for zero-downtime updates or A/B testing scenarios.
- ✗
Use Azure Traffic Manager to route traffic between the old and new versions.
Why it's wrong here
Azure Traffic Manager operates at the DNS level, routing user requests to different service endpoints based on various methods like performance or geographic proximity. While it can direct traffic between distinct application deployments, it introduces higher latency due to DNS resolution and is primarily suited for global traffic distribution or disaster recovery, not for rapid, low-latency, in-region blue/green deployments or A/B testing within a single App Service instance.
- ✓
Use deployment slots with swapping.
Why this is correct
Deployment slots allow you to deploy to a staging slot, test it, and then swap with the production slot. You can also route a percentage of traffic to the staging slot for A/B testing. Swapping back is immediate and provides a fast rollback.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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