🧱 Architecture Overview
🌐 Networking Layer
Custom VPC
Public subnets (for ALB & NAT Gateway)
Private subnets (for EC2 instances)
Internet Gateway
Route tables for controlled traffic flow
⚖️ Load Balancing
Application Load Balancer (ALB)
Target groups with health checks
Listener forwarding traffic to healthy EC2 instances
🔄 Compute & Scaling
Launch Template with:
AMI
Security groups
User data script
Auto Scaling Group:
Min, max, desired capacity
CPU-based scaling policies
Multi-AZ EC2 placement
🐳 Application Deployment
Django web app
Docker installed via EC2 user data
Container launched automatically at instance startup
🔐 Security Design
EC2 instances do not have public IPs
Instances are reachable only via ALB
Private subnets isolate application servers
NAT Gateway allows:
Docker image pulls
OS updates
Outbound internet access only
This aligns with least-exposure security principles.
🧪 Testing & Validation
✅ High Availability Test
Application remains accessible via ALB
Individual EC2 instance failure does not break the app
Traffic automatically reroutes to healthy instances
🔄 Autoscaling Test
Load generated using Apache JMeter
CPU-based scaling policies evaluated
Observed that CPU alone may not reflect real traffic load
Highlights need for memory / request-based metrics in production
🔐 Private Access Test
Direct SSH blocked due to private subnet placement
EC2 Instance Connect Endpoint used for secure access
No public exposure of application servers
🏁 Conclusion
Day 24 demonstrates how real production web platforms are built on AWS.
This is not about launching a single EC2 instance — it’s about:
Availability
Fault tolerance
Security
Scalability
Automation
By combining ALB, Auto Scaling Groups, private networking, and Docker, Terraform enables a robust, enterprise-grade hosting solution.
This project forms a strong foundation for extending into full three-tier architectures with databases, caching, and CI/CD pipelines.
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