# Iii Architecture Patterns

Use when composing iii primitives into backend architectures: durable workflows...

- Repository: https://github.com/iii-hq/iii (18876 stars)
- Category: Engineering
- License: see repository
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add iii-hq/iii --skill iii-architecture-patterns -g -a claude-code -y`
Codex: `npx skills add iii-hq/iii --skill iii-architecture-patterns -g -a codex -y`
Cursor: `npx skills add iii-hq/iii --skill iii-architecture-patterns -g -a cursor -y`
Gemini CLI: `npx skills add iii-hq/iii --skill iii-architecture-patterns -g -a gemini-cli -y`

## Description

Use when composing iii primitives into backend architectures: durable workflows, reactive backends, observer side effects, agentic pipelines, event-driven CQRS, effect pipelines, and trigger-transform-action automation.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Architecture Patterns

Use this skill when the task is larger than one function or trigger. Pick the pattern from the
requirement, then implement it with `Function`, `Trigger`, `Worker`, observers, state, queues,
streams, and pub/sub.

## Pattern Map

| Requirement | Pattern | iii shape |
| --- | --- | --- |
| Sequential work with retries, DLQ, step tracking | Durable workflow | Functions chained through named queues, progress in state |
| Keep views, metrics, cache, or clients in sync | Reactive backend | State triggers plus stream/pubsub side effects |
| React to another function's calls, results, or failures without changing it | Observer side effect | `iii.observe({ function_id, on, filters }, target)` (`iii-observe`) |
| Specialized AI agents hand work to each other | Agentic backend | One function per agent, queue handoffs, shared state |
| Commands publish events and projections update independently | Event-driven CQRS | Command functions, event log in state, subscribe triggers |
| Pure, traceable composition | Effect pipeline | Small functions composed synchronously with `trigger()` |
| Webhook/cron automation chains | Low-code automation | Trigger, transform, action nodes chained by enqueue |

## Durable Workflow

Use named queues when steps need different retry, FIFO, or concurrency policy.

### TypeScript

```typescript
import { registerWorker, TriggerAction } from "iii-sdk";

const iii = registerWorker("ws://localhost:49134", { workerName: "order-workflow" });

async function track(orderId: string, step: string, status: string) {
  await iii.trigger({
    function_id: "state::update",
    payload: { scope: "orders", key: orderId, ops: [{ type: "merge", path: ["steps"], value: { [step]: status } }] },
  });
}

The rest: https://github.com/iii-hq/iii/blob/HEAD/skills/iii-architecture-patterns/SKILL.md