Overview
The log end offset (LEO) is the offset of the next message that will be appended to a replica's log. The high watermark (HWM) marks what is committed: all in-sync replicas have replicated up to it, and only committed messages are given out to consumers. The leader may have a few messages at the end of its log, between the HWM and its LEO, that are not yet replicated. The HWM cannot advance while the ISR is smaller than min.insync.replicas. Consumers using isolation.level=read_committed are limited further, to the last stable offset.
Analogy
Production tip
Check yourself
Why can consumers only read up to the high watermark?
Sources
- Design (4.2 documentation) (opens in a new tab)
- KIP-966: Eligible Leader Replicas (opens in a new tab)
- Broker configs (4.2 documentation) (opens in a new tab)
- Monitoring (4.2 documentation) (opens in a new tab)
- KafkaConsumer Javadoc (4.2) (opens in a new tab)
Checked against Kafka 4.2 documentation on Oct 2026. Draft: not yet reviewed by a Kafka specialist. Releases move on, so confirm against the current documentation before you act on a number.