Use when load-testing a site's or API's critical endpoints — the "performance budget test" NFR checklists ask for but a Lighthouse-only audit never exercises, since Lighthouse simulates exactly one user. Works on any HTTP-reachable site or API (k6 by default, Artillery as alternative). Trigger on "load test this", "how does this hold up under traffic", "stress test the API", "set up performance budget tests", or when an NFR audit flags load-testing as unverified. NOT for browser-rendering performance (use nfr-gap-audit's baseline or production-cwv-review). NOT against production without explicit, scoped authorization — real load has real cost and risk; always confirm target, intensity, and time window first, and prefer staging when available.