CI/CD Pipeline Best Practices: From Code Push to Production in Under 10 Minutes

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

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

jobs:
  # Run all checks in parallel — don't wait for each other!
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20, cache: npm }  # Cache node_modules!
      - run: npm ci --prefer-offline
      - run: npm run lint
    # Typical: 45 seconds

  type-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20, cache: npm }
      - run: npm ci --prefer-offline
      - run: npx tsc --noEmit
    # Typical: 30 seconds

  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20, cache: npm }
      - run: npm ci --prefer-offline
      - run: npm test -- --coverage
    # Typical: 2-3 minutes

  build:
    runs-on: ubuntu-latest
    needs: [lint, type-check, test]  # Only build if all checks pass
    steps:
      - uses: actions/checkout@v4
      - uses: docker/setup-buildx-action@v3
      - uses: docker/build-push-action@v5
        with:
          cache-from: type=gha    # GitHub Actions cache for Docker layers!
          cache-to: type=gha,mode=max
          push: true
          tags: my-image:${{ github.sha }}

  deploy:
    runs-on: ubuntu-latest
    needs: build
    if: github.ref == 'refs/heads/main'  # Only deploy from main
    steps:
      - run: |
          # Blue-green deploy: create new stack, shift traffic, delete old
          aws ecs update-service --service my-api --force-new-deployment

# Node.js dependency caching
- uses: actions/setup-node@v4
  with:
    node-version: 20
    cache: npm                     # Cache ~/.npm (not node_modules!)
- run: npm ci --prefer-offline     # Uses cache, fast
# Without cache: 45s to install. With cache: 5s.

# Python caching
- uses: actions/setup-python@v5
  with:
    python-version: '3.12'
    cache: pip

# Docker layer caching — biggest Docker build speedup
- uses: docker/build-push-action@v5
  with:
    cache-from: type=gha           # Read from GitHub Actions cache
    cache-to: type=gha,mode=max   # Write to GitHub Actions cache
# First build: 4 minutes. Subsequent (no code change): 20 seconds.

# Order Dockerfile layers for maximum cache hit:
# COPY package.json .    ← changes weekly
# RUN npm ci             ← cached unless package.json changed
# COPY src/ .            ← changes per commit (last!)

# The test pyramid for fast CI:
#
#        /\    E2E tests: 5-10 tests
#       /  \   Run in CI on main only, not every PR
#      /----\  (Playwright, Cypress)
#     /      \
#    /--------\  Integration tests: 50-100 tests
#   /          \ Test API routes, DB queries, service contracts
#  /------------\ Run on every PR, target < 2 min total
# /              \
#/----------------\ Unit tests: 500-2000 tests
#                    Fast, isolated, no I/O
#                    Run on every commit, target < 30s

# Split tests by speed in CI:
# Fast job (every commit): unit tests only
# Slower job (every PR): unit + integration
# Nightly job: E2E full suite

# Parallelize test files:
- run: npx jest --maxWorkers=4 --testPathPattern=unit