AZ-305 Design infrastructure solutions Practice Question
A company is deploying a web application that must scale out automatically based on CPU usage. The application runs on Azure App Service. Which Azure feature should they configure?
⚠ Common exam trap
Many candidates confuse load-balancing services (Front Door, Load Balancer, Traffic Manager) with autoscaling, but only Autoscale rules directly adjust the number of compute instances based on a metric like CPU usage.
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
✓
Autoscale rules
Autoscale rules in Azure App Service allow the application to automatically increase or decrease the number of instances based on CPU usage metrics. This is the correct feature for scaling out a web application horizontally in response to load, as it directly adjusts the instance count of the App Service Plan.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Autoscale rules
Why this is correct
Autoscale rules are the only option that directly modifies the compute capacity of the App Service plan. They let you configure scale conditions based on runtime metrics such as CPU percentage, request queue length, or a custom Application Insights metric, and you can set minimum and maximum instance counts. When a metric threshold is breached, the service adds or removes instances to keep the app responsive, and you can even schedule scale actions for known load patterns.
- ✗
Azure Front Door
Why it's wrong here
Azure Front Door is a global, multi-region HTTP/S reverse proxy that handles traffic before it reaches the App Service. It performs SSL offload, URL-based routing, caching, and Web Application Firewall inspection, but it does not monitor the CPU or memory of your backend instances and cannot change how many instances are running. Even if Front Door absorbs some peak load via caching, it still forwards the rest to a fixed set of backends, so you still need autoscale rules to scale the App Service platform itself.
- ✗
Azure Load Balancer
Why it's wrong here
Azure Load Balancer is a layer-4 (TCP/UDP) forwarding service that distributes connection flows across a statically defined backend pool of virtual machines or scale-set instances. It conducts health probes and NAT rules, but it has no visibility into HTTP application metrics like CPU or request latency, and it never adds or removes instances from the pool. In an App Service context, a load balancer is not a substitute for scaling out—it only spreads load evenly to existing instances.
- ✗
Azure Traffic Manager
Why it's wrong here
Azure Traffic Manager works at the DNS resolution level and returns an endpoint based on routing priority, performance, or geography, using periodic HTTP/HTTPS health checks. It does not inspect the actual application traffic and never collects CPU, memory, or request queue metrics, so it has no awareness of capacity utilization. Its sole job is steering clients to a chosen front-end; any scale-out needed to handle the traffic must be handled by an autoscale rule attached to the App Service plan.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 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-305 exam.