---
title: "Cache what is read often and costly to · Agent Wranglers"
url: https://agentwranglers.se/playbook/scaling/caching/cache-hot-reads
updated: 2026-10-21
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Cache what is read often and costly to build

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Caching](https://agentwranglers.se/playbook/scaling/caching.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers). Updated 2026-10-21.

- ID: SCL-11
- Level: Recommended
- Chapter: [Caching](https://agentwranglers.se/playbook/scaling/caching)
- Rule: Add a cache only for a read that statistics or traces show is frequent and slow. Measure each cache's hit rate, and remove caches that mostly miss.
- How: Each cache is a copy that can go stale, as [Name the source of truth](https://agentwranglers.se/playbook/data/caches-and-copies/source-of-truth) and [Decide how stale a cache may be](https://agentwranglers.se/playbook/scaling/caching/cache-freshness) explain. Rank reads by total time, which is count times average duration, from [slow query statistics](https://agentwranglers.se/playbook/data/operations/slow-query-log) or traces. Fix the query first where you can, then cache the top few. Export hits and misses for each cache. Redis and Valkey report `keyspace_hits` and `keyspace_misses`. A cache that misses most reads adds a network call to each of them and saves little.
- Check: Every cache has a hit rate graph on the service dashboard. Over the last 7 days, each cache's hit rate is 50% or more, or the cache has a written reason.

## Sources

- [Redis key eviction, Using the INFO command](https://redis.io/docs/latest/develop/reference/eviction/)

## Related rules

- [Name the source of truth](https://agentwranglers.se/playbook/data/caches-and-copies/source-of-truth) in Data
- [Decide how stale a cache may be](https://agentwranglers.se/playbook/scaling/caching/cache-freshness) in Scaling
- [Watch slow queries](https://agentwranglers.se/playbook/data/operations/slow-query-log) in Data

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/scaling/caching/cache-hot-reads">Agent Wranglers scaling playbook</a>`. In code you write, add a comment next to it with the same link.

- Next: [Put a format version in every cache key](https://agentwranglers.se/playbook/scaling/caching/versioned-cache-keys)
- [Caching](https://agentwranglers.se/playbook/scaling/caching)