🧠 What is Azure App Service?

Azure App Service is a fully managed PaaS to host:

• Web apps (REST APIs, websites)
• Backend services
• Containers

👉 You don’t manage servers, OS patches, or runtime installs.

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🧱 High-Level Architecture

User / Client
   |
   | HTTPS
   |
Azure Front Door (optional)
   |
Azure App Service
   |
App Service Plan (compute)
   |
Application Code
   |
Logs / Metrics / Monitoring

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PART 1️⃣ Core Concepts (Very Important)

1️⃣ App Service vs App Service Plan

Component	Meaning
App Service	Your application
App Service Plan	Compute (CPU, RAM, scaling)

👉 Multiple apps can share one plan.

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2️⃣ Supported Runtimes

• Node.js
• Python
• Java
• .NET
• PHP
• Go (via container)
• Docker containers

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PART 2️⃣ Create Azure App Service (Portal)

STEP 1️⃣ Create Resource Group

Azure Portal → Resource Groups → Create

Field	Value
Name	rg-app-demo
Region	Central India / East US

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STEP 2️⃣ Create App Service

Create resource → Web App

Basics Tab

Setting	Value
Resource Group	rg-app-demo
Name	demo-api-123
Publish	Code
Runtime	Node.js 18 / Python 3.11
OS	Linux
Region	Same as RG

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STEP 3️⃣ Create App Service Plan

Setting	Value
Name	asp-demo-linux
SKU	B1 (Dev/Test)
OS	Linux

👉 You pay for App Service Plan, not app count.

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STEP 4️⃣ Create

⏳ Takes ~1 minute

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PART 3️⃣ Deploy an Application

OPTION A️⃣ Deploy via GitHub (Recommended)

1️⃣ Connect GitHub Repo

App Service → Deployment Center → GitHub

✔ Select repo ✔ Select branch (main) ✔ Azure auto-creates GitHub Actions

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2️⃣ Example Node.js App

// index.js
const express = require("express");
const app = express();

app.get("/", (req, res) => {
  res.json({ status: "App Service working 🚀" });
});

app.listen(process.env.PORT || 3000);

// package.json
{
  "scripts": {
    "start": "node index.js"
  }
}

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3️⃣ Deployment Flow

git push
  ↓
GitHub Actions
  ↓
Build
  ↓
Deploy to App Service

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OPTION B️⃣ Deploy via ZIP (CLI)

zip -r app.zip .
az webapp deploy \
  --resource-group rg-app-demo \
  --name demo-api-123 \
  --src-path app.zip

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PART 4️⃣ Configure App Settings (Environment Variables)

App Service → Configuration → Application settings

Key	Value
NODE_ENV	production
DB_HOST	private-db

Access in code:

process.env.DB_HOST

👉 No redeploy needed.

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PART 5️⃣ Logs, Monitoring & Debugging

1️⃣ Enable Log Streaming

App Service → Logs

✔ Application logging: ON ✔ Log level: Information

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View Logs (CLI)

az webapp log tail \
  --resource-group rg-app-demo \
  --name demo-api-123

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2️⃣ Application Insights

App Service → Application Insights → Enable

Tracks:

• Requests
• Errors
• Latency
• Dependencies

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PART 6️⃣ Scaling (Vertical & Horizontal)

Vertical Scaling (Change SKU)

App Service Plan → Scale up

SKU	Use
B1	Dev
S1	Production
P1v3	High traffic

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Horizontal Scaling (Auto-scale)

App Service Plan → Scale out

Example rule:

• CPU > 70% → add instance
• CPU < 30% → remove instance

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PART 7️⃣ Deployment Slots (Zero Downtime)

STEP 1️⃣ Create Slot

App Service → Deployment slots → Add

Slot	Purpose
staging	Test
production	Live

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STEP 2️⃣ Deploy to Staging

• GitHub Action deploys to staging

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STEP 3️⃣ Swap

Slots → Swap

✔ Zero downtime ✔ Instant rollback

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PART 8️⃣ Networking & Security (Production-Grade)

1️⃣ Restrict Public Access

Networking → Access restrictions

Allow:

• Office IP
• VPN
• Azure services only

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2️⃣ VNet Integration (Outbound)

Networking → VNet integration

Use when:

• Access private DB
• Call private APIs

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3️⃣ Private Endpoint (Inbound)

Networking → Private Endpoint

✔ App accessible only via VPN / VNet ✔ No public internet exposure

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PART 9️⃣ Custom Domain & HTTPS

Custom domains → Add

Steps:

1. Add DNS record (CNAME / A)
2. Bind domain
3. Enable HTTPS (free SSL)

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PART 🔟 Backup & Restore

App Service → Backups

• Schedule daily backups
• Store in Blob Storage
• Restore with 1 click

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PART 1️⃣1️⃣ Validate Everything

Check App

curl https://demo-api-123.azurewebsites.net

✔ Response OK

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Check Logs

az webapp log tail ...

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Check Scaling

Metrics → CPU / Memory

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🧠 Common Mistakes (Avoid These)

Mistake	Fix
Using Free tier for prod	Use S1+
Hardcoding secrets	Use App Settings / Key Vault
No health checks	Enable health probe
No slots	Always use staging
No monitoring	Enable App Insights

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🏁 Final Mental Model

App Service Plan = Engine
App Service      = Car
Deployment Slot  = Gearbox
App Settings     = Fuel
Monitoring       = Dashboard

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