---
title: "Name the source of truth · Agent Wranglers"
url: https://agentwranglers.se/playbook/data/caches-and-copies/source-of-truth
updated: 2026-10-20
licence: "All rights reserved"
---

# Name the source of truth

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Required
- Chapter: [Caches and copies](https://agentwranglers.se/playbook/data/caches-and-copies)
- Rule: For every piece of data, one store is the source of truth. Caches, search indexes and replicas are copies that can be rebuilt from it.
- How: Write down which store owns each kind of data. Never write only to a copy. Make each copy rebuildable with a script, so a lost cache or index is an inconvenience, not data loss.
- Check: Empty the cache and drop the search index on staging, then run the rebuild. The app works and shows the same results.

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers data playbook: https://agentwranglers.se/playbook/data/caches-and-copies/source-of-truth`.

- Next: [Decide how stale a cache may be](https://agentwranglers.se/playbook/data/caches-and-copies/cache-freshness)
- [Caches and copies](https://agentwranglers.se/playbook/data/caches-and-copies)