App Service plans
What it is
An App Service plan is the container and billing unit for one or more App Service apps. It defines the pricing tier (SKU), the compute capacity / worker size, the number of instances (scaling), and available features. Every web app, API, or Functions app on that plan shares its resources.
Why it exists
You need a consistent, predictable compute container that hosts apps and can scale. The plan centralizes size + tier + scale decisions: pick a tier (Free → Premium) for features, and scale up (resize) or out (add instances) at the plan level, which affects every app in it.
Key ideas
- Pricing tiers (examples): Free/Shared, Basic (production, no autoscale — manual scale only, up to 3 instances), Standard (autoscale, staging slots, backups), Premium (more capacity, more instances, private endpoints), Isolated (dedicated VNet, network isolation) — and newer Premium v3 / P0v3 with memory-optimized and Pay-as-you-go.
- Scaling: scale up (bigger SKU/worker → more RAM/CPU per instance) vs scale out (more instances — autoscale rules allowed from Standard tier).
- Plan determines feature limits: deployment slots, autoscale (min/max rules), VNet integration, custom domains, and zone redundancy mostly appear in paid tiers.
- Multiple apps can share one plan (saves cost) — but they compete for resources; a heavy app can starve others.
- App Service Environment (ASE) runs plans in a dedicated regional/zone VNet for hard network isolation.
How it fits (diagram)
Exam notes
- Autoscale on App Service requires Standard (or higher) tier; Free/Shared/Basic lack autoscale.
- Choose tier by feature needs — not every feature is in every tier (AZ-104 asks which features each tier supports).
- Zone redundancy on plans is available for select tiers and regions.
- Scaling the plan scales all apps it hosts; isolate critical apps on their own plan.
- AZ-104: “pick a plan tier, scale up/out, understand shared-plan contention.”
Related
Path MOC · app-service · virtual-machine-scale-set
📘 Source: Microsoft Learn — App Service Plan