Authors k6 JavaScript load-test scripts (VU loops + checks + sleeps), configures the `options` block with `stages` (ramp-up patterns) and `thresholds` (p(95) latency, error rate), runs via `k6 run script.js` or `--vus / --duration` ad-hoc flags, and uses thresholds as the CI pass/fail signal. Includes a latency-percentile interpretation reference: tail ratio (p99/p50), bimodal-distribution detection, coordinated omission and why naive p99 is optimistic, and constant-vus vs constant-arrival-rate executors. Use when the project ships HTTP / WebSocket / gRPC load tests and the team wants developer-friendly JavaScript authoring, or when a k6 threshold passes but the system still feels slow.