Apache Kafka® and ClickHouse® are open-source technologies that complement each other well. While Apache Kafka is great at handling real-time data feeds, it's not optimized for accessing large chunks of data or acting as an OLAP engine. On the other hand, ClickHouse is a scalable and reliable storage solution designed to handle petabytes of data and perform fast online analytical processing. By combining both technologies, users can create a performant data warehouse in ClickHouse that stays up-to-date by constantly receiving fresh data from Apache Kafka. This integration allows for efficient handling of real-time data feeds while also enabling powerful analytics capabilities on large volumes of historical data.