Why Your CI/CD Pipeline is Probably Too Slow (And How to Fix It)

Is your team waiting minutes (or hours) for builds to complete? Here's how to dramatically speed up your CI/CD pipeline without sacrificing quality.

The Common Problems

# Typical slow CI pipeline
name: Build and Test
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Install dependencies
        run: npm install
      - name: Run tests
        run: npm test
      - name: Build
        run: npm run build

This simple pipeline can take 5-10 minutes. Let's fix that.

Quick Wins

1. Cache Dependencies

# GitHub Actions example
steps:
  - uses: actions/checkout@v3
  - uses: actions/cache@v3
    with:
      path: |
        ~/.npm
        node_modules
      key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
  - run: npm ci

2. Parallel Test Execution

jobs:
  test:
    strategy:
      matrix:
        chunk: [1, 2, 3, 4]
    steps:
      - uses: actions/checkout@v3
      - run: |
          npx jest --shard=${{ matrix.chunk }}/4

Advanced Optimizations

1. Docker Layer Caching

# Bad: Everything changes with code
FROM node:alpine
COPY . .
RUN npm install
RUN npm run build

# Better: Layer optimization
FROM node:alpine
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

2. Selective Testing

jobs:
  determine_changes:
    runs-on: ubuntu-latest
    outputs:
      backend_changed: ${{ steps.filter.outputs.backend }}
      frontend_changed: ${{ steps.filter.outputs.frontend }}
    steps:
      - uses: dorny/paths-filter@v2
        id: filter
        with:
          filters: |
            backend:
              - 'backend/**'
            frontend:
              - 'frontend/**'

  backend_tests:
    needs: determine_changes
    if: ${{ needs.determine_changes.outputs.backend_changed == 'true' }}
    runs-on: ubuntu-latest
    steps:
      - run: npm test

Real World Examples

Before Optimization

Total Pipeline Time: 15 minutes
- Checkout: 30s
- Install deps: 3m
- Lint: 2m
- Test: 5m
- Build: 3m
- Deploy: 1.5m

After Optimization

Total Pipeline Time: 4 minutes
- Checkout: 30s
- Install deps: 30s (cached)
- Lint: 1m (parallel)
- Test: 1.5m (parallel)
- Build: 30s (cached)
- Deploy: 1m

Implementation Strategy

1. Caching Configuration

# .github/workflows/build.yml
jobs:
  build:
    steps:
      # NPM cache
      - uses: actions/cache@v3
        with:
          path: ~/.npm
          key: npm-${{ hashFiles('package-lock.json') }}
      
      # Build cache
      - uses: actions/cache@v3
        with:
          path: .next
          key: next-${{ github.sha }}

2. Test Splitting

// jest.config.js
module.exports = {
  maxWorkers: process.env.CI ? 2 : '50%',
  testSequencer: './testSequencer.js'
};

// testSequencer.js
class CustomSequencer {
  sort(tests) {
    const copyTests = Array.from(tests);
    const chunkSize = Math.ceil(copyTests.length / 4);
    const chunk = process.env.JEST_CHUNK || 1;
    return copyTests.slice(
      (chunk - 1) * chunkSize,
      chunk * chunkSize
    );
  }
}

Monitoring Build Times

1. Build Time Dashboard

// build-metrics.js
const metrics = {
  recordBuildTime: (job, duration) => {
    console.log(`${job}: ${duration}ms`);
    // Send to monitoring system
  }
};

// Usage in CI
console.time('build');
// ... build steps
console.timeEnd('build');

2. Trend Analysis

SELECT 
  date_trunc('day', timestamp) as day,
  avg(duration) as avg_duration,
  count(*) as build_count
FROM ci_builds
GROUP BY day
ORDER BY day DESC
LIMIT 30;

Best Practices

1. Smart Test Running

steps:
  - uses: actions/checkout@v3
    with:
      fetch-depth: 2
  
  - name: Get changed files
    id: changed
    run: |
      echo "::set-output name=files::$(git diff --name-only HEAD^ HEAD)"
  
  - name: Run affected tests
    if: contains(steps.changed.outputs.files, 'src/')
    run: npm test -- --findRelatedTests ${{ steps.changed.outputs.files }}

2. Dependency Management

{
  "scripts": {
    "preinstall": "node ./scripts/check-lock-file.js",
    "postinstall": "node ./scripts/clean-deps.js"
  }
}

Common Pitfalls to Avoid

1. Running all tests always
2. Not using build caches
3. Sequential job execution
4. Unnecessary installations
5. Large Docker images

Results

Our clients have seen:

• 70% reduction in build times
• 50% less CI runner costs
• Improved developer productivity
• Faster deployments
• Better test reliability

Conclusion

Fast CI/CD pipelines are possible with:

• Smart caching
• Parallel execution
• Selective testing
• Build optimization
• Regular monitoring

Remember: Every minute saved in CI is multiplied by your team size and daily builds.