Optimise Tasks

Moonrepo Optimise Tasks

Overview

Use this skill to improve task performance safely: measure first, optimize second, verify impact third.

When to Use

• CI or local runs are trending slower.
• Cache hit rate is low or unstable.
• Task graph execution does more work than expected.

Optimization Workflow

1. Measure baseline first

   moon run :test --affected
   moon run :build --affected
   

   Capture elapsed time and scope.
2. Check cache behavior
   • Verify cache inputs/outputs in task configs.
   • Confirm environment-dependent inputs are explicit.
3. Use graph-aware execution
   • Prefer --affected and project selectors for incremental workflows.
   • Avoid broad all-project runs for PR validation unless required.
4. Tune one variable at a time
   • Change one task config dimension (inputs, outputs, deps, args).
   • Re-measure with same scope.

Slow-Task Checklist

• Is the task running on too many projects?
• Are inputs too broad (invalidating cache constantly)?
• Are outputs missing (preventing cache reuse)?
• Are dependency edges causing unnecessary upstream runs?
• Is CI invoking non-affected full scans unnecessarily?

Anti-Patterns

• Optimizing before collecting baseline metrics.
• Changing multiple task knobs at once.
• Clearing cache as first response to every issue.
• Treating local and CI data as interchangeable without evidence.

Caveats

• Some speed regressions are toolchain/runtime regressions, not moon configuration.
• A faster run that skips required work is not an optimization; it is a correctness bug.