3-Tier Architecture Diagram

🌐 Internet
🌐 Internet
→
IGW
→
Public Subnet
VPC: empty-vpc (10.1.0.0/16)
Internet Gateway (IGW)
NAT Gateway + EIP
Public Subnet
AZ: ap-southeast-1a
CIDR: 10.1.1.0/24
🖥️ Public EC2
(Web Server - Nginx)
t2.micro
🛡️ Security Group: ec2-sg
• HTTP (80) ← Internet
• HTTPS (443) ← Internet
• SSH (22) ← Internet
Port 80/443
→
Nginx
→
Port 5000
📦 S3: Frontend Files
three-tier-web-app-satya/frontend
Private Subnets
Subnet 1 (AZ: ap-southeast-1b)
CIDR: 10.1.2.0/24
🖥️ Private EC2
(Flask Backend)
t2.micro
🛡️ Security Group: private-sg
• Port 5000 ← Public EC2
• SSH (22) ← Public EC2
Flask API
→
Port 5432
→
PostgreSQL
📦 S3: Backend Files
three-tier-web-app-satya/backend
Subnet 2 (AZ: ap-southeast-1c)
CIDR: 10.1.3.0/24
🗄️ RDS PostgreSQL
(Database)
db.t3.micro
🛡️ Security Group: rds-sg
• Port 5432 ← Private EC2
• No Outbound Access
SQL Queries
→
Database
🔐 IAM Role: ec2-s3-access-role
• S3 Access • SSM Session Manager
EC2 Instances
→
S3 Bucket

🔄 Detailed Traffic Flow:

🌐 Internet
→
IGW
→
Public Subnet
→
Nginx (Port 80)
Public EC2
→
Private Subnet
→
Flask (Port 5000)
Private EC2
→
RDS (Port 5432)
→
PostgreSQL DB
Private EC2
→
NAT Gateway
→
IGW
→
S3 / Internet

Legend:

VPC
Subnets
EC2 Instances
RDS Database
Gateways
S3 Storage

📊 Resource Summary:

Compute: 2 EC2 instances
Database: 1 RDS PostgreSQL
Network: 1 VPC, 3 Subnets
Security: 3 Security Groups
Gateways: 1 IGW, 1 NAT Gateway
Storage: 1 S3 Bucket