2nd/10_Wiki/Topics/Backend/Serverless_Computing.md

---
id: wiki-2026-0508-serverless-computing
title: Serverless Computing
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [FaaS, Function-as-a-Service, Lambda]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [serverless, cloud, faas, backend]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: typescript
  framework: aws-lambda/cloudflare-workers
---

# Serverless Computing

## 매 한 줄
> **"매 server 관리 없이 event 단위로 코드를 실행"**. 매 2014 AWS Lambda 출시로 본격화. 매 2026 현재 Cloudflare Workers, Vercel Edge, AWS Lambda + Function URLs 의 edge-native serverless 가 mainstream — cold start 의 sub-10ms.

## 매 핵심

### 매 모델 비교
- **Container (ECS, Cloud Run)**: long-lived, scale-to-N. Cold start 100ms-2s.
- **Lambda (region)**: per-invocation, max 15min. Cold start 100-500ms.
- **Edge (Workers, Vercel)**: V8 isolate, sub-millisecond cold start, max 30s CPU.
- **Durable (Durable Objects, Lambda + DynamoDB)**: stateful + serverless.

### 매 trade-offs
- **장점**: pay-per-use, auto-scale, ops-free.
- **단점**: vendor lock-in, cold start, debugging 어려움, time/memory limit.

### 매 응용
1. API endpoint (Hono on Workers).
2. Event processing (S3 → Lambda → SNS).
3. Cron job (EventBridge schedule).
4. WebSocket (API Gateway + Lambda).
5. ML inference (Lambda + container image, 10GB).

## 💻 패턴

### AWS Lambda (TypeScript)
```ts
import { APIGatewayProxyHandler } from 'aws-lambda';

export const handler: APIGatewayProxyHandler = async (event) => {
  const body = JSON.parse(event.body ?? '{}');
  const result = await processOrder(body);
  return { statusCode: 200, body: JSON.stringify(result) };
};
```

### Cloudflare Workers (Hono)
```ts
import { Hono } from 'hono';

const app = new Hono<{ Bindings: { DB: D1Database } }>();

app.get('/users/:id', async (c) => {
  const id = c.req.param('id');
  const user = await c.env.DB.prepare('SELECT * FROM users WHERE id = ?').bind(id).first();
  return c.json(user);
});

export default app;
```

### Cold start mitigation (provisioned concurrency)
```yaml
# serverless.yml
functions:
  api:
    handler: handler.api
    provisionedConcurrency: 5  # always-warm
    reservedConcurrency: 100   # max parallel
```

### Idempotent handler
```ts
const seen = new Map<string, any>();
export const handler = async (event: { id: string; data: any }) => {
  if (seen.has(event.id)) return seen.get(event.id);
  const result = await process(event.data);
  seen.set(event.id, result);
  return result;
};
// Production: use DynamoDB or Redis for cross-invocation idempotency
```

### Edge function (Vercel)
```ts
export const config = { runtime: 'edge' };

export default async function handler(req: Request) {
  const url = new URL(req.url);
  const cached = await caches.default.match(req);
  if (cached) return cached;
  const data = await fetch(`${process.env.UPSTREAM}${url.pathname}`);
  const resp = new Response(data.body, { headers: { 'cache-control': 'max-age=300' } });
  await caches.default.put(req, resp.clone());
  return resp;
}
```

### Durable Object (stateful)
```ts
export class Counter {
  constructor(private state: DurableObjectState) {}
  async fetch(req: Request) {
    let count = (await this.state.storage.get<number>('n')) ?? 0;
    count++;
    await this.state.storage.put('n', count);
    return new Response(String(count));
  }
}
```

### Event-driven (S3 → Lambda)
```python
def handler(event, context):
    for record in event['Records']:
        bucket = record['s3']['bucket']['name']
        key = record['s3']['object']['key']
        process_image(bucket, key)
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Low traffic API | Lambda or Workers |
| Global low-latency | Cloudflare Workers / Vercel Edge |
| Long-running (>15min) | Container (Cloud Run, Fargate) |
| Stateful realtime | Durable Objects |
| Heavy ML inference | Lambda container image or SageMaker |

**기본값**: Cloudflare Workers + Hono + D1 — 2026 의 best-DX serverless.

## 🔗 Graph
- 변형: [[FaaS]]
- 응용: [[API Gateway]] · [[Event-Driven Architecture]]
- Adjacent: [[Microservices]]

## 🤖 LLM 활용
**언제**: handler boilerplate, IAM policy 생성, cold start 분석.
**언제 X**: cost optimization (cloud bill 의 actual 측정 필요).

## ❌ 안티패턴
- **Lambda monolith**: 1 function 의 multi-route → cold start blast radius.
- **Sync chain**: Lambda A calls Lambda B sync — double charge + timeout risk.
- **No timeout**: default 3s 의 leak.
- **Heavy init**: connection pool init at handler 매 invoke → 매번 cold.

## 🧪 검증 / 중복
- Verified (AWS docs, Cloudflare docs, Vercel docs 2026).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Serverless 2026 state |