Apache Kafka 4.0 Release: Default KRaft, Queues, Faster Rebalances

What this post added

Apache Kafka 4.0 defaults to KRaft mode, deprecates ZooKeeper, and introduces a new consumer rebalance protocol for faster rebalances. Queues for Kafka (early access) enable traditional queue semantics. Eligible Leader Replicas (ELR) and Pre-Vote mechanisms enhance KRaft stability. Client metrics collection is extended, and duration-based offset reset is supported. Group administration is improved with new command-line tools. Client resilience is enhanced with rebootstrap capabilities. Support for old client protocol API versions, message formats v0/v1, and Java 8 is dropped. Kafka Streams allows foreign key extraction from both key and value in KTable joins, custom processor wrapping, and adds a 'retry' return-option to ProductionExceptionHandler.