Microservices-based digital wallet and payment system built with Java 17, Spring Boot 3, Spring Security, Hibernate, MySQL, RabbitMQ and Docker. Key Features: • 3 independent microservices (auth, wallet, notification) each with own database • Pessimistic locking for safe concurrent balance updates • Idempotent transactions via unique keys — zero duplicate payments • Deadlock prevention through ordered wallet locking • Event-driven notification pipeline using RabbitMQ • Comprehensive testing with JUnit 5 and Mockito • Containerized with Docker and Docker Compose for one-command deployment