What is KRaft mode in Kafka?

KRaft (Kafka Raft) is Kafka's built-in metadata management system, where a dedicated set of controller nodes inside the Kafka cluster itself — using the Raft consensus protocol — store and replicate cluster metadata (which brokers exist, which partitions live where, current leaders) instead of relying on an external system.

As of Apache Kafka 4.0 (released March 2025), KRaft is the only supported mode — the older external metadata-coordination approach has been fully removed from the codebase, not just deprecated, so every current Kafka deployment runs on KRaft.

# server.properties (KRaft mode)
process.roles=broker,controller
node.id=1
controller.quorum.voters=1@localhost:9093

In smaller deployments, a broker can also serve as a controller (combined mode); larger clusters typically run a small, dedicated set of controller-only nodes separate from the brokers that serve client traffic, since the controller quorum is now the most operationally critical component in the cluster.

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