Azure App Service is a service used to create and deploy scalable, mission-critical web apps.
Your App Service plan can be scaled up and down at any time. It is as simple as changing the pricing tier of the plan. You can choose a lower pricing tier at first and scale up later when you need more App Service features.
For example, you can start testing your web app in a Free App Service plan and pay nothing. When you want to add your custom DNS name to the web app, just scale your plan up to Shared tier. Later, when you want to create a TLS binding, scale your plan up to Basic tier. When you want to have staging environments, scale up to Standard tier. When you need more cores, memory, or storage, scale up to a bigger VM size in the same tier.
Pricing tier of an App Service plan
Shared compute: Free and Shared, the two base tiers, runs an app on the same Azure VM as other App Service apps, including apps of other customers. These tiers allocate CPU quotas to each app that runs on the shared resources, and the resources cannot scale out.
Dedicated compute: The Basic, Standard, Premium, PremiumV2, and PremiumV3 tiers run apps on dedicated Azure VMs. Only apps in the same App Service plan share the same compute resources. The higher the tier, the more VM instances are available to you for scale-out.
App Service Plan Tiers usage
Microsoft is advising on how / when you should the different App Service Plan tiers:
Free -> test and discover the hosting service
Shared -> basic apps with low traffic and not business critical
Basic -> dev and test of apps before production
Standard -> apps in production
Premium -> large scale apps in production
Refer- https://learn.microsoft.com/en-us/azure/app-service/overview-hosting-plans
https://medium.com/@zaab_it/azure-app-service-plan-tiers-f07d5e22297a
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