Intermediate5 min
Understanding HWM vs LEO
Read the log end offset and the high watermark on each partition and see what they mean for consumers.
The log end offset (LEO) is where the next record will be written. The high watermark (HWM) is the offset up to which all in-sync replicas have the data, and consumers are only given records below it. The leader may hold records beyond the HWM, up to its LEO, that are not replicated yet. The HWM cannot advance while the ISR is smaller than min.insync.replicas.
The steps use the simulator and name the control to use. The outcomes they describe are what the simulator models; the sources below are what Apache documents.
Steps
0 of 4 steps completed
Verification
You can read LEO, HWM and each group's position from the Offsets tab and explain how they relate.
The interview angle
The HWM is the boundary of what consumers are given; the LEO is where the next write goes. Records between them are on the leader but not yet replicated to the whole ISR.
Sources
- Design (4.2 documentation) (opens in a new tab)
- Broker configs (4.2 documentation) (opens in a new tab)
- Consumer configs (4.2 documentation) (opens in a new tab)
Checked against Kafka 4.2 documentation on 11 October 2026. Draft: not yet reviewed by a Kafka specialist, and releases move on, so confirm against the current documentation before you act on it.