Apache Kafka 3.9 Release: Dynamic KRaft Quorums, Better ZK Migration

What this post added

Introduces Dynamic KRaft Quorums (KIP-853) allowing dynamic addition/removal of controller nodes via tooling or AdminClient API, improving operational flexibility for KRaft mode. Enhances ZooKeeper migration tooling, making Kafka 3.9 the final and best iteration before ZooKeeper mode is removed in 4.0. Makes Tiered Storage (KIP-405) production-ready with new features like dynamic disablement (KIP-950), quotas (KIP-956), and exposed remote offsets (KIP-1005). Adds Kafka Streams config for log summary interval (KIP-1049) and an exception handler (KIP-1033). Kafka Connect improves null handling in transformations (KIP-1040), adds offset control in MirrorSourceConnector (KIP-1031), and introduces a health check endpoint (KIP-1017).