Three-tier AWS architecture separates web, application, and database layers across public and private subnets within a VPC. Internet traffic flows through an Application Load Balancer to an Auto Scaling Group of EC2 instances in the application tier. The database tier uses RDS PostgreSQL with a read replica for high availability, while S3 serves static assets. This pattern demonstrates AWS best practices for fault tolerance, horizontal scaling, and security isolation. Fork this diagram on Diagrams.so to customize instance types, add caching layers, or adapt for your workload.