We use Kafka as the data backbone to build Milvus, an open-source vector database system that has been adopted by thousands of organizations worldwide for vector similarity search. In this presentation, we will share how Milvus uses Kafka to enable both real-time processing and batch processing on vector data at scale. We will walk through the challenges of unified streaming and batching in vector data processing, as well as the design choices and the Kafka-based data architecture.