Apache Kafka 4.0 drops Zookeeper — KRaft is now the default

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.