Hassan M.

Java | Fintech Architect | HL7-FHIR Healthcare Interoperability

I architect backend systems in Java where mistakes are expensive — payment platforms that can't lose or duplicate a transaction, and healthcare systems that must exchange data correctly under HL7/FHIR and stay HIPAA-compliant. This isn't general backend development; it's architecture-level work in two domains where correctness, compliance, and reliability are the actual deliverable. Fintech & Payment Architecture: Built Spring Boot microservices for an Online Payment System integrated with the Ericsson Wallet Platform, supporting Raast QR-based transaction flows and processing 50k+ transactions. Designed a multi-service architecture (integration, transaction, merchant, and shared common services) connected via Feign clients over a shared database, with Kafka handling batch payment processing. Diagnosed and resolved a production Kafka issue where a topic silently failed on a specific exception — implemented bounded retries with dead-letter-queue routing after 5 failed attempts, so a bad message gets isolated instead of blocking the pipeline or risking a duplicate/lost transaction. Healthcare Interoperability: Engineered scalable healthcare microservices in Spring Boot, improving API response times by 40%. Built a 4-service pipeline (data processor, HIPAA/HL7-FHIR data handler, report generator, and cron-driven scheduler) connected via RabbitMQ, ingesting from both SFTP feeds and the patient portal database. Integrated HealthiPass for patient payment/engagement and a JasperReports-based report engine for automated patient reporting. Integrated AI-powered virtual agents and multichannel communication (Twilio SMS/IVR, NodeMailer) for patient engagement, with async orchestration via Azure Service Bus and BullMQ (Redis) improving throughput 3x. AI Pipelines & Automation: Contributed to an AI-powered interview assistant with ATS integrations (Zoho Recruit, Pinpoint) for candidate scoring and data sync. Built lead-capture and outreach automation using Zapier and n8n, and an n8n workflow connecting Slack to OpenToClose for real estate transaction task automation. Stack: Core: Java, Spring Boot, Spring Cloud, microservices architecture Payments: Payment gateway integration, transaction processing, merchant onboarding, idempotency and retry design Healthcare: HL7, FHIR, HIPAA-compliant data handling, patient data pipelines Data & Messaging: PostgreSQL, MongoDB, Redis, Kafka, RabbitMQ, Azure Service Bus APIs & Integrations: REST API design, webhook management, ATS integrations DevOps: Docker, CI/CD, Grafana/CloudWatch monitoring, distributed tracing Automation: n8n, Zapier, AI agent integrations How I work: I start by understanding what has to never fail — a transaction, a compliance requirement, a data exchange — and design the architecture around that constraint first. Every system ships with retry logic, dead-letter handling, and observability built in, because in fintech and healthcare, silent failure isn't an option. If your project involves payment systems, Kafka-based event processing, or healthcare data that needs to move correctly between systems, that's exactly where I work best.