Multi-account AWS organization architecture for a Korean fintech stablecoin settlement hub spanning DMZ, VDI, development, and production VPCs across ap-northeast-2 with Transit Gateway connectivity. Internet traffic flows through Route 53, AWS WAF, and AWS Shield in the DMZ account, with Fortinet FortiGate VMs providing hybrid on-premises integration via Transit Gateway. Development and production workloads run on separate accounts with ALB-fronted EC2 instances (t3.medium dev, m5.xlarge prod) backed by RDS and Aurora databases in private subnets across two availability zones. VDI account provides secure remote access via Amazon Workspaces with AD Connector and FIDO2 MFA, while the Common Account centralizes security monitoring through GuardDuty, AWS Config, Inspector, Security Hub, and Trend Micro Deep Security. This architecture demonstrates defense-in-depth for regulated fintech workloads, isolating security and operational concerns across dedicated accounts with centralized logging to S3 Object Lock WORM and OpenSearch analytics. Fork and customize this diagram on Diagrams.so to adapt the multi-account strategy, adjust instance types, or modify VPC CIDR ranges for your settlement infrastructure.