Event-driven Spring Boot 3 microservices with Kafka: producers, consumers, retries and dead-letter topics

Spring Boot 3 enables event-driven microservices using Spring Kafka to handle OrderPlaced events between orders and inventory services. To prevent partition blocking, developers implement retries with back-off and dead-letter topics (DLT). For reliable validation, Testcontainers integrates with JUnit 5 and Spring Boot 3.1+, utilizing @ServiceConnection to launch real PostgreSQL and Kafka instances in Docker. This approach ensures that SQL queries and JSON serialization function correctly in production-like environments, surpassing the limitations of mocks or H2.