Commercial payment platform sequence diagram orchestrating merchant authentication, onboarding, e-transfer processing, and settlement across six phases on AWS. Merchant Client connects via React/Angular Dashboard to AWS Cognito OAuth 2.0, Spring Boot REST API, and Payment Engine, with Apache Kafka Event Bus enabling async fan-out to Invoicing Service and Reporting Module backed by PostgreSQL RDS and Redis Cache. Architecture demonstrates 30% onboarding effort reduction and 28% peak load reduction through event-driven design, independent service scaling, and caching strategies. Fork this diagram on Diagrams.so to customize authentication flows, add payment gateways, or adapt for your compliance requirements. OSFI-compliant immutable event logging via Kafka ensures regulatory audit trails for Canadian financial institutions.