---
title: "Kafka cleanup.policy=compact,delete: both policies at once"
description: "Compaction removes the stale A=a1 while retention.ms deletes B=b1 by age, though b1 is the latest value of B. The two Kafka cleanups run independently."
url: https://monedula.dev/kafka-simulator/scenarios/compact-delete-policy/
---

# Kafka cleanup.policy=compact,delete: both policies at once

Scenario 05.2.3 · compact,delete policy. Storage · Intermediate · about 3 min · Apache Kafka 4.3.

A topic running both policies: compaction collapses duplicate keys while time retention independently ages out the old log prefix.

Run it: https://monedula.dev/kafka-simulator/playground/?scenario=05.2.3

## What you start with

cleanup.policy=compact,delete runs both cleanups on one topic at once: compaction collapses duplicate keys down to their latest value, while time-based retention independently ages out and deletes the old log prefix.

## Step by step

1. **compact,delete topic (empty)** (t+0.000s): A topic with cleanup.policy=compact,delete runs BOTH policies. Compaction collapses to the latest value per key; retention.ms (1500ms) independently deletes records older than the window. The two are orthogonal. [Open at this step](https://monedula.dev/kafka-simulator/playground/?scenario=05.2.3&t=0)
2. **Old batch · A=a1, B=b1** (t+0.200s): The old batch lands: A=a1 at offset 0 and B=b1 at offset 1, both timestamped ~100ms. They are still young relative to the 1500ms retention window. [Open at this step](https://monedula.dev/kafka-simulator/playground/?scenario=05.2.3&t=1)
3. **Recent batch · A→a2, C=c1** (t+1.620s): A recent batch updates A to a2 (offset 2) and adds C=c1 (offset 3). Key A now has two records in the log - a compaction target - while B and C have one each. [Open at this step](https://monedula.dev/kafka-simulator/playground/?scenario=05.2.3&t=2)
4. **Compacted · stale A=a1 collapsed** (t+1.700s): Compaction pass - the COMPACT half. A collapses to its latest value a2; the stale A=a1 at offset 0 is removed (note the offset gap). B and C are untouched - compaction never deletes a key's latest record. Real Kafka never compacts the active segment, so these records would first have to roll into a closed one. [Open at this step](https://monedula.dev/kafka-simulator/playground/?scenario=05.2.3&t=3)
5. **Retention · aged-out B=b1 deleted** (t+2.100s): Retention sweep - the DELETE half. With retention.ms=1500, B=b1 (timestamped ~100ms) is now too old, so the aged prefix is deleted and logStartOffset advances past it, even though b1 was B's only record. Real Kafka deletes whole segments by their newest timestamp, so this assumes b1's segment holds nothing newer. A=a2 and C=c1 survive both policies. [Open at this step](https://monedula.dev/kafka-simulator/playground/?scenario=05.2.3&t=4)

## The takeaway

The two policies are independent - compaction bounds the log by distinct keys while delete-retention still trims by age, so old records leave even when their key holds the latest value.

## Configs in this scenario

- [`cleanup.policy`](https://kafka.apache.org/43/configuration/topic-configs/#topicconfigs_cleanup.policy): Whether old data is removed by age/size (delete), by keeping only the latest value per key (compact), or both - it decides whether the topic behaves like a stream or a keyed changelog. [How cleanup.policy works](https://monedula.dev/kafka-simulator/configs/cleanup-policy/)
- [`retention.ms`](https://kafka.apache.org/43/configuration/topic-configs/#topicconfigs_retention.ms): How long a topic with cleanup.policy=delete keeps a log segment before it may be deleted (default 604800000, 7 days); -1 removes the time limit. [How retention.ms works](https://monedula.dev/kafka-simulator/configs/retention-ms/)

## Further reading

- [Apache Kafka documentation](https://kafka.apache.org/43/configuration/topic-configs/#topicconfigs_cleanup.policy)