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aws-scalable-webapp-alb/AWS-SCALABLE-WEBAPP-ALB-README.md

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+# 🚀 AWS Scalable Web Application — ALB + ASG
+
+A production-grade, self-healing web application deployed on AWS using an Application Load Balancer, Auto Scaling Group, and EC2 across multiple Availability Zones. Mimics how platforms like **Heroku / Railway** manage scalable deployments automatically.
+
+---
+
+## 📸 Screenshots
+
+> All build screenshots are available in the [`/images`](./images) folder, numbered `1` through `81` in chronological build order.
+
+**Key screenshots inline:**
+
+### App Running via ALB DNS
+![App running via ALB](./images/aws-scalable-webapp-alb-63.png)
+> App served through the Application Load Balancer DNS — no direct EC2 IP
+
+### Target Group — Both Instances Healthy in different AZ's
+![Target group healthy](./images/aws-scalable-webapp-alb-43.png)
+> Both EC2 instances passing health checks across two Availability Zones
+
+### Auto Scaling Group — Instance Management after deleting 
+![ASG instances](./images/aws-scalable-webapp-alb-65.png)
+> ASG maintaining desired capacity across `ap-south-1a` and `ap-south-1b` after terminating an ec2 machine to check for auto healing
+
+### AWS Notification -Subscription email
+![Email subscription confirmation for cloudwatch notification](./images/aws-scalable-webapp-alb-78.png)
+
+![CONFIRMED](./images/aws-scalable-webapp-alb-79.png)
+>Confirmed notification subscription
+
+### CloudWatch Monitoring Dashboard
+![CloudWatch dashboard](./images/aws-scalable-webapp-alb-81.png)
+> Real-time metrics — CPU, request count, response time, instance count
+
+----
+
+## 🏗️ Architecture
+
+```
+Internet
+    │
+    ▼
+Internet Gateway (scalable-webapp-igw)
+    │
+    ▼
+┌─────────────────────────────────────────────────────────┐
+│  VPC: scalable-webapp-vpc (10.0.0.0/16)                 │
+│                                                         │
+│  ┌──────────────────┐     ┌──────────────────┐          │
+│  │ public-subnet-1a │     │ public-subnet-1b │          │
+│  │  10.0.1.0/24     │     │  10.0.2.0/24     │          │
+│  └──────────────────┘     └──────────────────┘          │
+│            │                        │                   │
+│            ▼                        ▼                   │
+│   Application Load Balancer (webapp-alb)                │
+│            │  HTTP :80 Listener                         │
+│            ▼                                            │
+│   Target Group (webapp-target-group)                    │
+│    ├──▶ EC2 t3.micro — ap-south-1a  ✓ healthy           │
+│    └──▶ EC2 t3.micro — ap-south-1b  ✓ healthy           │
+│              ▲                                          │
+│    Auto Scaling Group (webapp-asg)                      │
+│    min: 1 │ desired: 2 │ max: 4                         │
+│    CPU > 50% → scale out                                │
+│    CPU < 30% → scale in                                 │
+│              │                                          │
+│    Launch Template (webapp-launch-template)             │
+│    Amazon Linux 2023 + nginx                            │
+└─────────────────────────────────────────────────────────┘
+```
+
+---
+
+## ⚙️ AWS Services Used
+
+| Service | Purpose |
+|---|---|
+| **VPC** | Isolated network with public subnets across 2 AZs |
+| **EC2** | Compute — runs nginx web server |
+| **Application Load Balancer** | Distributes traffic, health checks, single DNS entry |
+| **Auto Scaling Group** | Automatically adds/removes instances based on CPU |
+| **Launch Template** | Blueprint for identical EC2 instances |
+| **IAM Role** | EC2 permissions for S3 and CloudWatch |
+| **CloudWatch** | Metrics dashboard + CPU alarm via SNS email |
+| **Security Groups** | Layered firewall — ALB faces internet, EC2 accepts ALB only |
+
+---
+
+## 🔐 Security Design
+
+```
+Internet → alb-sg (HTTP 0.0.0.0/0)
+                ↓
+           ec2-sg (HTTP from alb-sg ONLY)
+```
+
+EC2 instances are **not directly reachable** from the internet. All public traffic flows through the ALB only. This is a standard production security pattern.
+
+---
+
+## 📦 Infrastructure Summary
+
+### VPC & Networking
+| Resource | Value |
+|---|---|
+| VPC CIDR | `10.0.0.0/16` |
+| Public Subnet 1 | `10.0.1.0/24` — ap-south-1a |
+| Public Subnet 2 | `10.0.2.0/24` — ap-south-1b |
+| Internet Gateway | Attached to VPC |
+| Route Table | `0.0.0.0/0 → IGW` |
+
+### Compute
+| Resource | Value |
+|---|---|
+| AMI | Amazon Linux 2023 |
+| Instance Type | t3.micro |
+| Web Server | nginx |
+| Deployment | User data script on launch |
+
+### Auto Scaling
+| Setting | Value |
+|---|---|
+| Minimum | 1 |
+| Desired | 2 |
+| Maximum | 4 |
+| Scale-out trigger | CPU > 50% |
+| Scale-in trigger | CPU < 30% |
+
+### Monitoring
+| Resource | Value |
+|---|---|
+| Dashboard | `webapp-monitoring` |
+| Alarm | `webapp-high-cpu` — triggers at 70% |
+| Notification | SNS email alert |
+
+---
+
+## 🛠️ Build Phases
+
+| Phase | What was built |
+|---|---|
+| 1 — Networking | VPC, subnets, IGW, route table, security groups |
+| 2 — Compute | Launch template, IAM role, test EC2, nginx + web app |
+| 3 — Auto Scaling | ASG with target tracking scaling policy |
+| 4 — Load Balancer | ALB, target group, listener, ASG integration |
+| 5 — Monitoring | CloudWatch dashboard, CPU alarm, SNS notification |
+
+---
+
+## 💡 Key Cloud Concepts Demonstrated
+
+- **High Availability** — workload spread across 2 Availability Zones
+- **Horizontal Scaling** — ASG adds instances under load, removes them when idle
+- **Self-healing Infrastructure** — failed instances are automatically replaced by ASG
+- **Security Layering** — EC2 not exposed directly, traffic flows ALB → EC2 only
+- **Infrastructure as a Blueprint** — Launch Templates ensure every instance is identical
+- **Observability** — CloudWatch dashboard + proactive alerting via SNS
+
+---
+
+## 🧹 Cleanup
+
+To avoid AWS charges after testing:
+
+1. Delete **Auto Scaling Group** (this terminates all EC2 instances)
+2. Delete **Application Load Balancer**
+3. Delete **Target Group**
+4. Delete **Launch Template**
+5. Delete **CloudWatch Alarms and Dashboard**
+6. Delete **VPC** (also removes subnets, IGW, route tables, security groups)
+7. Delete **IAM Role** `ec2-webapp-role`
+8. Delete **SNS Topic** `webapp-cpu-alert`
+
+---
+
+## 📁 Repository Structure
+
+```
+aws-scalable-webapp-alb/
+├── index.html          # Web app deployed on EC2 via nginx
+├── README.md           # This file
+└── images/             # All build screenshots (1–70, in chronological order)
+```
+
+---
+
+##  Learning Journey
+
+Built as part of a hands-on AWS Cloud & DevOps learning journey.