Glossary

Log retention (Kafka)

Kafka log retention controls how long messages are kept on disk before deletion. It can be configured by time (`log.retention.hours`), by size (`log.retention.bytes`), or both (whichever limit is reached first). Retention is enforced per partition at the segment level — Kafka only deletes closed (inactive) segments; the active segment being written is not deleted regardless of age until it rolls.

Formula: Low-volume partitions may need log.segment.ms to rotate segments so time retention applies; disk ≈ ingest × retention × RF (simplified).

Last updated: March 2026