Tips and Tricks #77: Cache Dependencies in GitHub Actions

Speed up CI builds by caching package manager dependencies between runs.

Code Snippet

# .github/workflows/ci.yml
name: CI
on: [push, pull_request]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - name: Cache node modules
        uses: actions/cache@v4
        with:
          path: ~/.npm
          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
          restore-keys: |
            ${{ runner.os }}-node-
      
      - name: Install dependencies
        run: npm ci
      
      - name: Run tests
        run: npm test

Why This Helps

• Reduces build time by 50-80%
• Saves CI minutes and costs
• Faster feedback loop for developers

How to Test

• Compare build times with and without cache
• Check cache hit rate in Actions logs

When to Use

Any CI pipeline with package dependencies. Works for npm, pip, Maven, Gradle, etc.

Performance/Security Notes

Use hashFiles() to invalidate cache when lockfile changes. Set appropriate restore-keys for partial matches.

References

• https://github.com/actions/cache

Try this tip in your next project and share your results in the comments!