Highly available three-tier web application architecture on AWS uses Application Load Balancer to distribute traffic across an Auto Scaling Group of t3.medium EC2 instances within a VPC. Application tier connects to RDS PostgreSQL Primary (db.t3.medium) for writes and RDS Read Replica for read queries, offloading database load while EC2 instances store and retrieve static assets from S3. Users access static content through CloudFront CDN for low-latency global delivery, reducing origin load and improving performance. Fork this diagram on Diagrams.so to customize instance types, add Multi-AZ deployment, or integrate ElastiCache for session management.