---
id: backend-cron-workflows-inngest
title: Inngest / Trigger.dev — function-as-a-workflow
category: Coding
status: draft
source_trust_level: B
verification_status: conceptual
created_at: 2026-05-09
updated_at: 2026-05-09
tags: [backend, workflow, vibe-coding]
tech_stack: { language: "TS", applicable_to: ["Backend"] }
applied_in: []
aliases: [Inngest, Trigger.dev, function workflow, durable function, event-driven, cron, retry]
---

# Inngest / Trigger.dev

> Modern async / cron / workflow. **Code 가 function, retry / step / wait 자동**. Temporal 의 simple version.

## 📖 핵심 개념
- Function = workflow.
- Step = retry / dedup unit.
- Event 가 trigger.
- Cron / wait 가 native.

## 💻 코드 패턴

### Inngest function
```ts
import { Inngest } from 'inngest';
const inngest = new Inngest({ id: 'my-app' });

export const dailyReport = inngest.createFunction(
  { id: 'daily-report' },
  { cron: '0 9 * * *' },
  async ({ event, step }) => {
    const data = await step.run('fetch', async () => fetchData());
    
    await step.sleep('wait', '1m');
    
    await step.run('email', async () => sendEmail(data));
    
    return { ok: true };
  }
);
```

→ 매 step 가 retry / dedup 자동.

### Event-triggered
```ts
export const onUserSignup = inngest.createFunction(
  { id: 'welcome-email' },
  { event: 'user/signup' },
  async ({ event, step }) => {
    await step.run('send', () => sendWelcome(event.data.email));
    
    await step.sleep('wait-3-days', '3d');
    
    await step.run('check-active', async () => {
      const user = await getUser(event.data.userId);
      if (!user.active) await sendReengagement(user);
    });
  }
);

// Trigger
await inngest.send({ name: 'user/signup', data: { userId, email } });
```

### Step.sleep (durable wait)
```ts
await step.sleep('wait', '1d');
// → Function 가 종료. 1 day 후 resume.
// → Server restart 가 OK (state durable).
```

→ Long-running workflow.

### Step.waitForEvent
```ts
const event = await step.waitForEvent('payment-confirmed', {
  event: 'payment/confirmed',
  match: 'data.userId',
  timeout: '1h',
});

if (!event) {
  // Timeout
}
```

→ "다음 event 가 도착 까지 wait".

### Trigger.dev
```ts
import { client } from './trigger';

client.defineJob({
  id: 'daily-report',
  trigger: cronTrigger({ cron: '0 9 * * *' }),
  run: async (payload, io) => {
    const data = await io.runTask('fetch', async () => fetchData());
    await io.sendEvent('email', { name: 'send', payload: { data } });
  },
});
```

→ Inngest 와 매우 비슷.

### Concurrency limit
```ts
{ concurrency: { limit: 10 } }
// → 10 instance max parallel.
```

### Throttle
```ts
{ throttle: { limit: 100, period: '1m' } }
// → 1 min 안 100 max.
```

### Retry policy
```ts
inngest.createFunction(
  { id: 'task', retries: 5 },
  ...
  async ({ step }) => {
    await step.run('flaky', async () => {
      // Auto retry 5 times.
    });
  }
);
```

### Cancel running function
```ts
{
  cancelOn: [{ event: 'user/deleted', if: 'event.data.userId == async.data.userId' }]
}
```

→ 외부 event 가 cancel.

### Local dev
```bash
npx inngest-cli dev
# → Dashboard at localhost:8288.
```

→ Function trace + replay + UI.

### Production deploy
```ts
// Vercel / Cloudflare / Lambda
// Inngest 가 serverless 친화.

// app/api/inngest/route.ts (Next.js)
import { serve } from 'inngest/next';
import { dailyReport, onUserSignup } from '../../inngest';

export const { GET, POST, PUT } = serve({
  client: inngest,
  functions: [dailyReport, onUserSignup],
});
```

### vs Temporal
```
Temporal:
- 강력 (workflow language).
- Self-host 가 가능.
- 큰 enterprise.
- Steeper.

Inngest:
- TS-friendly.
- Managed 친화.
- Simple.
- 작은 / 중간.

→ Modern serverless = Inngest.
큰 / on-prem = Temporal.
```

### vs BullMQ
```
BullMQ:
- Redis-backed.
- Self-host.
- 더 raw.

Inngest:
- Managed.
- Workflow primitive.
- Step / sleep native.

→ Inngest 가 더 production friendly.
```

### vs AWS Step Functions
```
Step Functions:
- AWS native.
- ASL (state machine).
- Managed scaling.

Inngest:
- TS code (no DSL).
- Multi-cloud.

→ AWS-only = Step Functions.
Multi-cloud / TS = Inngest.
```

### Use case
```
- Email sequence (welcome → 3 day → 7 day).
- LLM agent workflow.
- Image processing pipeline.
- Daily report.
- Subscription billing.
- Scheduled cleanup.
- Data sync (매 hour).
```

### LLM agent (Inngest)
```ts
export const agent = inngest.createFunction(
  { id: 'agent' },
  { event: 'agent/start' },
  async ({ event, step }) => {
    let context = event.data.task;
    
    for (let i = 0; i < 5; i++) {
      const action = await step.run(`think-${i}`, async () => llm.complete(...));
      
      if (action.type === 'done') return action.result;
      
      const result = await step.run(`act-${i}`, async () => execute(action));
      context += result;
    }
  }
);
```

→ Multi-step agent + retry / pause / resume.

### Idempotency
```ts
{
  idempotency: 'event.data.orderId',
}
// → 같은 orderId 의 event 가 1번만.
```

### Batching
```ts
{
  batchEvents: { maxSize: 100, timeout: '5s' }
}
// → 5 sec 또는 100 event 마다 batch.
```

### Cost
```
Inngest free: 1k step / month.
Pro: $20-200 / month.

Trigger.dev: 비슷.

→ Self-host alternative 가 BullMQ + cron.
```

### Anti-pattern
```
- Step 안에 step.run 가 안: nested 안 됨.
- Side effect 가 step.run 외: retry 시 중복.
- Long step (>30 sec): timeout (function level).
- Throw vs return error: 매 다름.
```

### Best practice
```
1. 매 side effect 가 step.run.
2. Idempotent step (key).
3. Concurrency / throttle (외부 API rate limit).
4. Timeout (긴 wait 도).
5. Error monitoring.
```

## 🤔 의사결정 기준
| 상황 | 추천 |
|---|---|
| Modern serverless | Inngest / Trigger.dev |
| 큰 / on-prem | Temporal |
| Self-host simple | BullMQ |
| AWS-only | Step Functions |
| LLM agent | Inngest (durable + retry) |
| Email sequence | Inngest (sleep) |

## ❌ 안티패턴
- **Side effect 가 step 외**: retry 중복.
- **Long sleep 가 step.sleep 안**: function timeout.
- **No idempotency**: replay 시 중복.
- **No concurrency limit**: external API 폭발.
- **Step 가 nested**: 안 됨.

## 🤖 LLM 활용 힌트
- Inngest = durable function + step.
- Cron / event / wait native.
- LLM agent 에 강함.
- Temporal 의 simple alternative.

## 🔗 관련 문서
- [[Backend_Cron_Scheduler_Patterns]]
- [[Backend_Job_Scheduling_Temporal]]
- [[Backend_Saga_Choreography_vs_Orchestration]]
