---
title: "System architecture · Agent Wranglers"
url: https://agentwranglers.se/playbook/architecture/system-architecture
parts: 5
tokens_total: 4620
updated: 2026-10-27
build: a2a6bdfed830
tokens: 725
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# System architecture

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

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-27.

> Set quality goals with numbers and check each decision in the build. Draw the system as code, and choose how its parts stay consistent and fail apart.

**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/architecture/system-architecture">Agent Wranglers clean code and architecture playbook</a>`. In code you write, add a comment next to it with the same link.

## Recommended

- ARC-86 [Write each quality goal as a scenario with a number](https://agentwranglers.se/playbook/architecture/system-architecture/quality-scenarios.md) · 838 tokens · updated 2026-10-27
  Write each quality goal that shapes the design as a scenario with a measure. Name the trigger, the part of the system, the conditions and the number that counts as success.
- ARC-87 [Check each architecture decision with a fitness function](https://agentwranglers.se/playbook/architecture/system-architecture/fitness-functions.md) · 1,104 tokens · updated 2026-10-27
  Turn each architecture decision that code can break into a test the build runs, called a fitness function. Module borders inside one app get one first.
- ARC-89 [Choose how fresh each piece of shared data must be](https://agentwranglers.se/playbook/architecture/system-architecture/consistency-model.md) · 872 tokens · updated 2026-10-27
  For each piece of data that two parts of the system read, write down the consistency it needs. Choose strong, read-your-writes or eventual, and give the longest delay you accept.
- ARC-90 [Give each outside dependency its own pool](https://agentwranglers.se/playbook/architecture/system-architecture/bulkheads.md) · 852 tokens · updated 2026-10-27
  Give each outside service the app calls its own connection pool or limit on calls at once. A slow or failing service then uses up only its own share.
- ARC-91 [Run a change across services as a saga with undo steps](https://agentwranglers.se/playbook/architecture/system-architecture/sagas.md) · 954 tokens · updated 2026-10-27
  When one business action changes data owned by two or more services, run it as a saga. Each step commits locally, and each step that can fail later has an undo step that runs on failure.

- Previous: [Concurrency](https://agentwranglers.se/playbook/architecture/concurrency.md)
- Next: [Technical debt](https://agentwranglers.se/playbook/architecture/technical-debt.md)
- [All chapters](https://agentwranglers.se/playbook/architecture.md)