Multi-AZ headless envelope processing server built on AWS with .NET Core ECS tasks, SQS/SNS event routing, and RDS MS SQL failover across us-east-1a and us-east-1b. Traffic flows through WAF and API Gateway to load-balanced ECS tasks that queue file checks via SQS, trigger Lambda processors, and publish status updates through SNS. The architecture ensures high availability with RDS primary-standby replication, ElastiCache Redis clustering, and dual ALBs across availability zones. This design solves envelope validation, file checking, and notification workflows while maintaining sub-second failover and audit compliance via CloudWatch Logs and S3. Fork and customize this diagram on Diagrams.so to adapt subnet ranges, instance types, or add additional Lambda processors for your document pipeline.