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Policy keys

recourse selects behavior using a policy key: a stable, low-cardinality identifier for a call site.

Examples:

  • ✅ "user-service.GetUser"
  • ✅ "payments.Charge"
  • ❌ "GET /users/123"
  • ❌ "user-service.GetUser?user_id=123"

Why low-cardinality matters:

  • Keys back caches/trackers (e.g., policy caches, latency trackers in later phases).
  • High-cardinality keys create unbounded memory and noisy telemetry.

Parsing

policy.ParseKey("svc.Method") yields policy.PolicyKey{Namespace:"svc", Name:"Method"}. If no dot is present, the entire string becomes Name and Namespace is empty.