Apache Kafka and Apache Cassandra may be written in JVM hosted languages, but they're widely used outside the JVM ecosystem. Kafka is a distributed append-only

Apache Kafka and Apache Cassandra may be written in JVM hosted languages, but they're widely used outside the JVM ecosystem. Kafka is a distributed append-only log widely used in data streaming. Cassandra is a distributed NoSQL datastore. Not sure why you raised that, though, given they're not mentioned in the linked article.