k6

k6 is a developer-centric, open-source load testing tool suitable for testing APIs, microservices, and websites. It is written in Go but you script tests in JavaScript.

When to Use

• API Load Testing: The gold standard for modern API performance testing.
• CI/CD Integration: Very lightweight binary (or Docker), easy to gate capabilities ("fail if p95 > 500ms").
• Developer Friendly: Uses JS (ES6) for scripting, so backend/frontend devs can write tests.

Quick Start

import http from "k6/http";
import { sleep, check } from "k6";