Cold start and premium plan in Azure - Commands & Configuration

Introduction

Cold start happens when a cloud function or app takes extra time to start because it was inactive. Premium plans help reduce this delay by keeping resources ready to respond quickly.

When your app or function is slow to respond after being idle for some time.

When you want faster response times for users even if your app is not used constantly.

When you have unpredictable traffic and want to avoid delays during sudden spikes.

When you want to pay for reserved resources to improve performance.

When you want to avoid cold start delays in serverless functions like Azure Functions.

Commands

This command creates a Premium plan named myPremiumPlan in the eastus region. The Premium plan helps reduce cold start delays by keeping resources warm.

Terminal

az functionapp plan create --name myPremiumPlan --resource-group exampleResourceGroup --location eastus --sku EP1 --is-linux false

Expected Output

{

  "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/exampleResourceGroup/providers/Microsoft.Web/serverfarms/myPremiumPlan",

  "location": "eastus",

  "name": "myPremiumPlan",

  "sku": {

    "name": "EP1",

    "tier": "PremiumV2"

  },

  "status": "Ready",

  "type": "Microsoft.Web/serverfarms"

}

→

--sku EP1 - Selects the Premium plan SKU to reduce cold start delays.

→

--is-linux false - Specifies the plan is for Windows-based apps.

This command creates a function app named myFunctionApp using the Premium plan myPremiumPlan. This setup helps the function app avoid cold start delays.

Terminal

az functionapp create --name myFunctionApp --storage-account mystorageaccount --plan myPremiumPlan --resource-group exampleResourceGroup --runtime dotnet

Expected Output

{

  "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/exampleResourceGroup/providers/Microsoft.Web/sites/myFunctionApp",

  "name": "myFunctionApp",

  "resourceGroup": "exampleResourceGroup",

  "state": "Running",

  "type": "Microsoft.Web/sites"

}

→

--plan myPremiumPlan - Associates the function app with the Premium plan.

→

--runtime dotnet - Sets the runtime environment for the function app.

This command shows details about the function app to confirm it is running on the Premium plan and ready to avoid cold starts.

Terminal

az functionapp show --name myFunctionApp --resource-group exampleResourceGroup

Expected Output

{

  "name": "myFunctionApp",

  "state": "Running",

  "serverFarmId": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/exampleResourceGroup/providers/Microsoft.Web/serverfarms/myPremiumPlan",

  "kind": "functionapp",

  "location": "eastus"

}

Key Concept

If you remember nothing else from this pattern, remember: Premium plans keep your app ready to respond fast by avoiding cold start delays.

Common Mistakes

Creating a function app without specifying a Premium plan.

The app will run on a consumption plan and experience cold start delays.

Always create or assign your function app to a Premium plan to reduce cold starts.

Using the wrong SKU name when creating the plan.

The plan will not be Premium and will not reduce cold start delays.

Use the correct SKU like EP1, EP2, or EP3 for Premium plans.

Summary

Create a Premium plan to keep resources warm and reduce cold start delays.

Create your function app using the Premium plan to improve response times.

Verify your function app is running on the Premium plan to ensure cold start is minimized.