1) Event-driven microservices involve microservices communicating primarily through events published to an event backbone. This loosely couples microservices and allows for eventual data consistency. 2) Apache Kafka is an open-source streaming platform that can be used to build an event backbone, allowing microservices to reliably publish and subscribe to events. It supports streaming, storage, and processing of event data. 3) Common patterns for event-driven microservices include database per service for independent data ownership, sagas for coordinated multi-step processes, event sourcing to capture all state changes, and CQRS to separate reads from writes.