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Kafka Is Fun

What Changed in Kafka 4.x

KRaft-only, the new rebalance protocol, share groups, Streams and tiered storage: what changed since Kafka 3.x, with every claim linked to an Apache source.

0 of 6 lessons complete

  1. 1Kafka 4.0: ZooKeeper Is GoneKafka 4.0, released in March 2025, is the first major release that runs entirely without Apache ZooKeeper. It supports o…
  2. 2Migrating from ZooKeeper to KRaftYou migrate on 3.9, not on 4.0, because the migration needs a release that still speaks ZooKeeper. The cluster moves thr…
  3. 3The New Consumer Rebalance Protocol (KIP-848)In the classic protocol every join, leave or failure sends the whole group through a synchronization barrier, and even c…
  4. 4Share Groups: Queues for Kafka (KIP-932)Share groups let several consumers read the same partitions at the same time and acknowledge each record on its own, whi…
  5. 5Kafka Streams in 4.x: Server-Side Rebalancing and Dead Letter QueuesKafka Streams gets the idea behind KIP-848. The Streams rebalance protocol (KIP-1071) is built on the new consumer group…
  6. 6Tiered Storage and Diskless Topics: What Is RealTiered storage, which keeps older log segments in remote storage, has been production-ready since Kafka 3.9. That releas…

Knowledge check

Q1.A cluster still runs in ZooKeeper mode. What does Kafka 4.0 require before you can upgrade it?

Q2.How does a consumer opt in to the KIP-848 rebalance protocol?

Q3.Why should you not plan around diskless topics (KIP-1150) today?