Three-tier AWS architecture separates web, application, and data layers across public and private subnets within a VPC. Users connect via HTTPS through an ALB that distributes traffic to EC2 instances in an Auto Scaling Group. The app tier writes to RDS PostgreSQL Primary while reads hit the Read Replica, with static assets served from S3. This pattern delivers high availability, read scalability, and security isolation for production workloads. Fork this diagram on Diagrams.so to customize instance types, add caching layers, or export as .drawio for your documentation.