What's changed: New GH-200 Chapter 5 (security best practices = script-injection mitigation, GITHUB_TOKEN least privilege vs PAT, OIDC cloud federation, SHA pinning/trustworthy actions/usage policies, attestations/provenance (SLSA), environment approval gates; performance/cost optimization = actions/cache, retention (REST API), matrix size/max-parallel, concurrency+cancel-in-progress, paths/branches filters, if conditions, runner sizing)
5.2Optimizing Performance and Cost
Understand efficiency via caching and artifact retention, applying retention policies via REST APIs, and strategies for scaling and cost-optimizing workflows—concurrency, matrix size, concurrency groups, runner selection, conditionals, and path/branch filters.
GitHub Actions usage is billed by execution minutes and storage (artifacts/cache). GH-200 tests optimizing for faster and cheaper runs without sacrificing results. The levers fall into "reduce waste (avoid unneeded runs/re-downloads)" and "tune parallelism and retention."
5.2.1Caching and retention
Caching (actions/cache)—avoiding dependency re-fetches—is the most effective speed-up (Chapter 1). Artifacts and logs have a retention period; keeping them longer increases storage billing—review defaults and shorten via retention-days at upload to cut cost. These retention policies are also applicable/inspectable via the REST API, enabling org-wide auto-deletion of stale data. Note caches have free-tier/size limits and old caches are evicted automatically.
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