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Apache Kafka 4.0 drops Zookeeper — KRaft is now the default

Kafka 4.0 is the first major release fully free of Zookeeper. KRaft mode is now the only option. Here's what changes for your cluster.

📅 2026-06-03
#kafka#big-data#release#open-source

What changed

Apache Kafka 4.0 ships without Zookeeper support. The KRaft (Kafka Raft) consensus protocol is now the only mode.

Why this matters

Zookeeper has been a pain point for years:

  • Separate cluster to manage and monitor
  • Metadata stored in ZK, not Kafka — created sync issues
  • Extra failure domain
  • More complex ops for small teams

KRaft moves all metadata management into Kafka itself. One less system to run.

Migration path

If you're still on Zookeeper-mode Kafka:

  1. Upgrade to Kafka 3.x first (supports both modes)
  2. Run the migration tool: kafka-zk-to-kraft-migration.sh
  3. Validate in staging
  4. Upgrade to Kafka 4.0

Kafka 3.9 is the last version supporting Zookeeper mode.

What stays the same

  • Client APIs unchanged — producers and consumers don't need updating
  • Same config for topics, partitions, replication
  • All major connectors (Debezium, MirrorMaker) work with KRaft

Bottom line

If you're on managed Kafka (Confluent Cloud, MSK, Aiven), you're likely already on KRaft. Self-hosted clusters need to plan the migration before upgrading past 3.9.

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