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Azure Fundamentals · Lesson

Autoscaling and Custom Domains

Configure scale-out rules based on CPU and HTTP queue metrics, map a custom domain to your web app, and bind a free App Service Managed Certificate.

Why Autoscaling Matters

Autoscaling automatically adjusts the number of App Service instances running your application based on real-time demand. Without autoscaling, you must provision for peak load and pay for idle capacity during off-peak hours. With autoscaling, Azure adds instances when load rises and removes them when it drops, optimising both performance and cost. Autoscaling requires Standard tier or above.

Scale-Out vs Scale-Up

Azure offers two scaling dimensions. Scale out (horizontal scaling) adds more identical instances of your app to share the load — this is what autoscaling primarily does. Scale up (vertical scaling) moves to a larger VM size with more CPU and RAM by changing the App Service plan SKU. Scale-out is preferred for resilience because multiple instances can survive individual failures; scale-up has hardware limits.

# Scale out to 5 instances manually
az appservice plan update \
  --name MyAppServicePlan \
  --resource-group MyRG \
  --number-of-workers 5

# Scale up: change the SKU tier
az appservice plan update \
  --name MyAppServicePlan \
  --resource-group MyRG \
  --sku P2V3

All lessons in this course

  1. Creating an App Service Plan and Web App
  2. Deployment Slots and Swap
  3. Autoscaling and Custom Domains
  4. App Service Authentication and Networking
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