The document discusses building event-driven microservices using Apache Kafka. It describes how microservices can interact asynchronously through events published to an event hub like Apache Kafka. This allows for loose coupling between services and the ability to integrate new services by consuming past events from the event log. The document also discusses how Apache Kafka can be used for change data capture from legacy systems, streaming data integration, and providing a unified platform for real-time event processing and historical analytics.