How would you design a CI/CD pipeline for a Next.js application with automated testing and deployment?

CI/CD Pipeline Architecture

Push → GitHub Actions → Build → Test → Deploy
                              ↓
                        Staging (auto)
                              ↓
                        Production (manual approval)

GitHub Actions Workflow

# .github/workflows/deploy.yml
name: CI/CD Pipeline

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

jobs:
  # Stage 1: Lint & Type Check
  validate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20 }
      - run: npm ci
      - run: npm run lint
      - run: npm run type-check

  # Stage 2: Tests
  test:
    needs: validate
    runs-on: ubuntu-latest
    services:
      mongodb:
        image: mongo:7
        ports: ["27017:27017"]
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npm run test:unit
      - run: npm run test:e2e
        env:
          DATABASE_URL: mongodb://localhost:27017/test

  # Stage 3: Build
  build:
    needs: test
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npm run build
      - uses: actions/upload-artifact@v4
        with:
          name: build
          path: .next/

  # Stage 4: Deploy to Staging (auto on develop)
  deploy-staging:
    needs: build
    if: github.ref == 'refs/heads/develop'
    runs-on: ubuntu-latest
    steps:
      - run: echo "Deploy to staging server"

  # Stage 5: Deploy to Production (manual on main)
  deploy-production:
    needs: build
    if: github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    environment: production  # Requires manual approval in GitHub
    steps:
      - run: echo "Deploy to production"

Pipeline Best Practices

Practice	Why
Fast feedback first (lint → test → build)	Fail fast, save compute
Service containers for DB	Real database for integration tests
Upload build artifacts	Don't rebuild in deploy step
Separate staging/prod	Catch environment issues
Manual prod approval	Human gate for production
Secrets via GitHub Secrets	Never commit credentials