This article presents an open-sourced event-driven architecture solution for processing ISO 20022 payment messages on AWS, designed for financial services organizations modernizing their payment infrastructure.

• ISO 20022 is a unified messaging standard replacing legacy formats like ISO 8583 and ISO 15022
• Solution supports multi-Region deployment with tunable consistency and failover capabilities
• Architecture uses microservices with Lambda, SQS, DynamoDB, and S3 for message processing workflows
• API consumers authenticate via Cognito OAuth 2.0 and submit transactions through regional endpoints
• Processing includes validation stages: technical, business, KYC, AML, fraud, and liquidity checks
• Cost scales from $16.6K/month at 100 TPS to $158.5K/month at 1,000 TPS
• Deployment uses Terraform, Terragrunt, and CodeBuild CI/CD pipeline
• Alternative architectures support ActiveMQ, RabbitMQ, Kinesis, or Kafka instead of SQS

The solution provides a scalable, serverless foundation for ISO 20022 payment processing with flexible deployment options and transparent cost modeling.