Three-tier web application architecture on AWS separates presentation, application logic, and data layers across isolated subnets within a VPC in us-east-1. Users access the application through CloudFront CDN and WAF, which routes traffic to an Application Load Balancer distributing requests across three EC2 t3.medium instances in an Auto Scaling Group within the private app tier subnet. Application servers connect to RDS PostgreSQL Primary db.t3.large for writes and RDS Read Replica for read operations in the data tier subnet, while static assets are served from S3 through CloudFront. This architecture demonstrates AWS best practices for high availability, security through network segmentation, and horizontal scalability for production web workloads. Fork this diagram on Diagrams.so to customize instance types, add additional availability zones, or integrate additional AWS services like ElastiCache or Route 53.