App Service plans
What it is
An App Service plan supplies the compute capacity and pricing tier for one or more compatible App Service apps. It determines the worker capacity, scale options, and supported features for those apps. Think of it as the shared hosting capacity; the web app is the site running on that capacity.
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
- Scale up changes the plan SKU or worker capacity. Scale out changes the number of plan instances. Both decisions can affect every app that shares the plan.
- Plan tiers offer different limits and features, such as scaling, deployment slots, networking, and availability options. SKU names and availability change, so check the current App Service plan documentation for a production choice.
- Sharing a plan can lower cost for small apps, but a busy or faulty app can compete with its neighbors for the same capacity. Put workloads with different performance, scaling, or isolation needs on separate plans.
- An App Service plan is not a VM pool you administer. Azure operates the workers; you select the capacity and app configuration.
Northwind example
Northwind places its ordering API and a small internal admin site on separate plans. A lunch-time surge makes the ordering API scale out; isolating it prevents that surge from consuming the admin site’s capacity. When Northwind tests a new plan SKU, it tests the application behavior and cost, not just whether the portal accepts the setting.
Common confusion
- Scaling a plan can affect all apps on it; scaling a single app may not be an available or equivalent option.
- A plan is not the same as a resource group, subscription, or deployment slot.
- The cheapest tier is not automatically the safest choice when a workload requires a feature or production capacity it does not support.
How it fits (diagram)
Design check
List the apps, expected traffic, isolation need, networking need, slot requirement, availability requirement, and budget before choosing a plan. Confirm each requirement against the current SKU documentation in the target region.
Related
app-service · deployment-slots · app-service-networking · virtual-machine-scale-set · northwind-traders-case-study
📘 Source: Microsoft Learn — App Service plans, checked 2026-09-16.