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

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 } }] },
  });
}