CI/CD: GitHub Actions → 자동 배포

# .github/workflows/ci.yml
name: CI

on:
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: pnpm/action-setup@v3
        with: { version: 9 }
      - uses: actions/setup-node@v4
        with:
          node-version: 20
          cache: pnpm

      - name: Install
        run: pnpm install --frozen-lockfile

      - name: Lint
        run: pnpm lint

      - name: Typecheck
        run: pnpm typecheck

      - name: Build
        run: pnpm build
        env:
          NEXT_PUBLIC_SUPABASE_URL: ${{ secrets.SUPABASE_URL_STAGING }}
          NEXT_PUBLIC_SUPABASE_ANON_KEY: ${{ secrets.SUPABASE_ANON_KEY_STAGING }}

      - name: Unit Tests
        run: pnpm test

  e2e:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: pnpm/action-setup@v3
      - uses: actions/setup-node@v4
        with: { node-version: 20, cache: pnpm }
      - run: pnpm install --frozen-lockfile
      - run: pnpm exec playwright install chromium
      - run: pnpm test:e2e

- main 브랜치 push → Vercel Production 자동 배포
- PR → Vercel Preview URL
- Vercel은 GitHub Action 외부에서 처리

# .github/workflows/migrate.yml
name: DB Migration

on:
  workflow_dispatch:  # 수동 트리거
    inputs:
      env:
        type: choice
        options: [staging, production]

jobs:
  migrate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: supabase/setup-cli@v1
        with: { version: latest }

      - name: Push migrations
        run: |
          supabase link --project-ref ${{ secrets.SUPABASE_PROJECT_REF_PROD }}
          supabase db push
        env:
          SUPABASE_ACCESS_TOKEN: ${{ secrets.SUPABASE_ACCESS_TOKEN }}

GitHub → Settings → Branches → Add rule for main
✓ Require status checks: ci.yml + e2e
✓ Require branches up to date
✓ Require linear history
✓ Include administrators (선택)

[코드 롤백]
Vercel → Deployments → 이전 성공 배포 → "Promote to Production"
즉시 롤백 (5초)

[DB 롤백]
- 마이그레이션은 forward-only가 안전
- 컬럼 추가는 nullable로
- 이전 버전 코드와 호환되도록 작성

// PostHog Feature Flag
import { useFeatureFlagEnabled } from 'posthog-js/react'

const isNewFeatureEnabled = useFeatureFlagEnabled('new-ai-feature')

return isNewFeatureEnabled ? <NewFeature /> : <OldFeature />

[Bottleneck]
- pnpm install: 1분
- TypeScript: 30초
- Build: 1-2분
- E2E: 3-5분

[최적화]
- pnpm cache (actions/cache)
- Turbo build (Turbopack)
- E2E 병렬 (--workers=4)
- 작은 커밋 단위 → 빠른 fix

// src/app/api/health/route.ts
export async function GET() {
  const supabase = await createClient()
  const { error } = await supabase.from('users').select('id').limit(1)

  if (error) return Response.json({ status: 'unhealthy' }, { status: 503 })
  return Response.json({ status: 'healthy', version: process.env.VERCEL_GIT_COMMIT_SHA })
}

[옵션]
- BetterStack Uptime: 무료 10 monitor
- Pingdom
- StatusCake

설정: GET https://mysaas.com/api/health
- 1분 간격 체크
- 에러 시 이메일·SMS·Slack