Building Enterprise Payment Systems

Aditya Deshpande is a Senior Software Engineer at PayPal with more than eight years of experience building and supporting enterprise applications. His work spans digital payments, transaction monitoring, chargeback processing, fraud and mismatch identification, RESTful services, microservice integration, performance engineering, and critical production support. He has developed backend systems with Java, Spring Boot, Spring MVC, Hibernate, relational and NoSQL databases, and has also contributed to React and JavaScript applications. Earlier in his career, he engineered service-management and workflow products using Java, Drools, multithreading, BPMN-oriented user interfaces, and Jenkins-based continuous integration. Aditya holds a Master of Science in Management Information Systems from Texas A&M University and a Bachelor of Engineering in Electronics and Telecommunication. He is a certified Professional Scrum Master and Professional Product Owner. His combination of hands-on payment-platform experience and broad enterprise-software engineering makes him well positioned to explain how reliable transaction systems are designed, implemented, tested, and operated.

Part I - Payment Systems as Enterprise Software.- Chapter 1: Enterprise Payment Platforms: Architecture, Ownership and Operational Truth.- Chapter 2: Payment Lifecycle, Domain Model, and State Integrity.- Chapter 3: Spring Boot Transaction Core and Payment APIs.- Part II - Building the Transaction Core.- Chapter 4: External Processor Integration and Reliable Outcomes.- Chapter 5: Event-Driven Processing, Idempotency, and Duplicate Suppression.- Chapter 6: Distributed Transactions, Sagas, Outbox, and Safe Reprocessing.- Chapter 7: Fraud Screening, Transaction Monitoring, and Investigation Workflows.- Part III - Distributed Reliability.- Chapter 8: Refunds, Disputes, Chargebacks, and Reconciliation.- Chapter 9: Security, Data Protection, Auditability, and  Financial Controls.- Chapter 10: Testing, Observability, Performance, and Incident Response.- Chapter 11: Deployment, Merchant Onboarding, Tenancy, and Partner APIs.- Part IV - Risk and Post-Payment Operations.- Chapter 12: Governance, Charge Control, Capstone, and Future Proofing.