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Amazon MSK Express Brokers support Kafka 4.2 with improved rebalancing

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feature patch

Amazon MSK Express Brokers now support Apache Kafka version 4.2, introducing enhancements for leader election correctness and a new consumer rebalance protocol for smoother, faster group rebalances. This update aims to bring the latest open-source reliability and performance improvements to MSK Express, which already offers significant throughput and scaling advantages. The support is available today for new and existing MSK Express clusters across all offered AWS regions.

  • →Support for Apache Kafka version 4.2 on MSK Express Brokers
  • →New Streams Rebalance Protocol for Kafka Streams
  • →Benefits of MSK Express Brokers
  • →Availability and Upgrade Options
Features (1) ›
  • Support for Apache Kafka version 4.2 on MSK Express Brokers

    Amazon MSK Express Brokers now support Apache Kafka version 4.2. This version includes enhancements such as Eligible Leader Replicas (ELR) for improved leader election correctness and a new consumer rebalance protocol designed for smoother and faster group rebalances.

Enhancements (1) ›
  • New Streams Rebalance Protocol for Kafka Streams

    A new Streams Rebalance Protocol has been introduced, extending broker coordination capabilities to Kafka Streams. This protocol aims to optimize task assignments for Kafka Streams applications.

Notes (2) ›
  • Benefits of MSK Express Brokers

    MSK Express Brokers are designed for high throughput, offering up to three times more throughput per broker, faster scaling up to 20 times, and a 90 percent reduction in recovery time. This update brings the latest open-source reliability and performance improvements to these enhanced brokers.

  • Availability and Upgrade Options

    Apache Kafka version 4.2 support is available today across all AWS regions where Amazon MSK Express Brokers are offered. Users can select version 4.2.x when creating new clusters or upgrade existing MSK Express Brokers via an in-place rolling update.

Read the original announcement →

https://aws.amazon.com/about-aws/whats-new/2026/07/aws-msk-express-version-42/

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