Once the Azure functions are developed and deployed to azure, then you pay per use pricing model. Azure function has below hosting plans - Dedicated app service plan
- Consumption plan
- Premium plan (called as elastic premium plan)
Azure functions Premium plan is a higher plan compared to other 2 plans. It contains following features - VNET Integration- To add more security to your app, you can configure a VNET and add your function app. With this, your function app is secured with service endpoints. VNET integration is not available in other plans.
- Pre-warmed instances to avoid cold start - In consumption plan, if there are no execution/calls to your function app it scales in to Zero instances. Once it goes to zero instances, if we make any function call, it takes some time(called as cold start time) to respond to the first call (from zero to one). This latency can be avoided in Premium plan with pre-warmed instances.
- Unlimited execution duration - Consumption plan has a 10 minutes limit whereas Premium plan defaults to 30 minutes but you can modify it to unlimited(60 minutes guaranteed). Use functiontTimeout property in host.json file to change the configuration.
- Premium hardware - Provides best cores(1, 2 and 4), memory and storage.
- Multiple function apps can be deployed to the same plan and all function apps in premium plan shares pre-warmed active instances.
- Automatic Scaling - Like consumption plan, your app will scale in or scale out based on the need.
Note: Premium plan is charged based on the number of core seconds, memory used and configured pre-warmed instances.
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