Middle/Senior Java Backend Developer (Payment Systems)

We are looking for a Senior Java Backend Developer to design, develop, and maintain high-performance backend services for our payment processing platform. You will work closely with cross-functional teams including Product, DevOps, and QA to deliver secure, scalable, and reliable payment solutions integrated with multiple payment gateways and partners.Key ResponsibilitiesDesign & Development:Build robust and scalable microservices using Java (Spring Boot / WebFlux) and RESTful APIs for payment transactions, reconciliation, and reporting.System Integration:Integrate with external payment gateways (e.g., MoMo, VNPAY, VETC, Stripe, PayPal) and internal wallet systems via APIs, SDKs, and secure messaging queues (Kafka/RabbitMQ).Database & Data Flow:Model and manage transactional data in PostgreSQL/MySQL, ensure data integrity, and optimize SQL performance for large-scale payment records.Security & Compliance:Implement PCI DSS-compliant practices, data encryption, and authentication/authorization (JWT, OAuth2) for financial-grade APIs.Performance & Reliability:Apply caching, async processing, and reactive programming for low-latency transaction handling and real-time payment status updates.Testing & Quality:Write comprehensive unit, integration, and regression tests using JUnit/Testcontainers; contribute to continuous integration (CI/CD) pipelines.Monitoring & Troubleshooting:Utilize tools like ELK/Prometheus/Grafana to monitor system health, latency, and error rates; ensure high availability and disaster recovery readiness.