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Cache-Based Skip

Skip operations when output artifacts already exist.

Hash-Based Cache Keys

Derive cache keys from source file hashes. Same source = same output = skip the build.

This implements the cache-based skip technique for GitHub Actions workflows.

Implementation

- name: Check cache
  id: cache
  uses: actions/cache@v4
  with:
    path: dist/
    key: build-${{ hashFiles('src/**') }}

- name: Build
  if: steps.cache.outputs.cache-hit != 'true'
  run: npm run build

The cache key is derived from source file hashes. Same source = same output = skip the build.

When to Use

  • Build artifacts - Skip compilation when source unchanged
  • Dependencies - Skip install when lockfile unchanged
  • Generated files - Skip generation when inputs unchanged

Key Considerations

  • Cache key design - Include all inputs that affect output
  • Cache invalidation - Know when to bust the cache
  • Partial hits - Handle cases where cache is stale

See the engineering pattern for conceptual details.

References

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