Caching & Matrix Builds

Cache dependencies

Caching the package manager's store avoids re-downloading dependencies on every run. setup-node can do it for you.

steps:
  - uses: actions/checkout@v4
  - uses: actions/setup-node@v4
    with:
      node-version: 22
      cache: npm          # restores ~/.npm keyed by package-lock.json
  - run: npm ci
  - run: npm test

Build matrix

A matrix runs the same job across several combinations in parallel.

jobs:
  test:
    runs-on: ${{ matrix.os }}
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, windows-latest]
        node: [20, 22]
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: "${{ matrix.node }}" }
      - run: npm ci && npm test

Key caches on lockfile hashes so they refresh when dependencies change. A matrix multiplies run time, so only include combinations you actually support.

Quick check

Quick check: What does a build matrix do?

• Runs a job across several combinations in parallel
• Encrypts secrets
• Deploys to production
• Deletes caches