AWS SaaS three-tier web application spanning Route 53, CloudFront, WAF, and ALB for global traffic ingestion across web, mobile, and third-party integrations. Application tier runs ECS Fargate microservices in private subnets across two availability zones with service discovery, auto-scaling, and secrets management via Cognito and Secrets Manager. Data tier isolates RDS PostgreSQL primary-replica, ElastiCache Redis, DynamoDB, and S3 storage in separate private subnets, with comprehensive observability via CloudWatch Logs and X-Ray. This architecture demonstrates high-availability SaaS patterns: multi-AZ redundancy, stateless compute, managed databases, and defense-in-depth security using IAM, KMS, CloudTrail, and AWS Config. Fork and customize this diagram on Diagrams.so to adapt subnet CIDR ranges, instance types, or add additional microservices and data stores.