k6-load-testing

k6 Load Testing

Overview

k6 is a modern, developer-centric load testing tool that helps you write and execute performance tests for HTTP APIs, WebSocket endpoints, and browser scenarios. This skill provides comprehensive guidance on writing realistic load tests, configuring test scenarios (smoke, load, stress, spike, soak), analyzing results, and integrating with CI/CD pipelines.

Use this skill when you need to validate system performance, identify bottlenecks, ensure SLA compliance, or catch performance regressions before deployment.

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When to Use This Skill

• Use when you need to load test HTTP APIs, WebSocket endpoints, or browser scenarios
• Use when setting up performance regression tests in CI/CD
• Use when analyzing system behavior under various load conditions
• Use when comparing performance between code changes
• Use when validating SLA requirements and performance budgets

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k6 Basics

Installation

# macOS
brew install k6

# Windows
choco install k6

# Linux
sudo gpg -k
sudo gpg --no-default-keyring --keyring /usr/share/keyrings/k6-archive-keyring.gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys C5AD17C747E3415A3642D57D77C6C491D6AC1D69
echo "deb [signed-by=/usr/share/keyrings/k6-archive-keyring.gpg] https://dl.k6.io/deb stable main" | sudo tee /etc/apt/sources.list.d/k6.list
sudo apt-get update
sudo apt-get install k6

Quick Start

// simple-test.js
import http from 'k6/http';
import { check, sleep } from 'k6';

export const options = {
  vus: 10,
  duration: '30s',
};

export default function () {
  const res = http.get('https://httpbin.test.k6.io/get');
  
  check(res, {
    'status is 200': (r) => r.status === 200,
    'response time < 500ms': (r) => r.timings.duration < 500,
  });
  
  sleep(1);
}

Run with: k6 run simple-test.js

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Test Configuration

Common Options

export const options = {
  // Virtual Users (concurrent users)
  vus: 100,
  
  // Test duration
  duration: '5m',
  
  // Or use stages for ramp-up/ramp-down
  stages: [
    { duration: '30s', target: 20 },   // Ramp up
    { duration: '1m', target: 100 },  // Stay at 100
    { duration: '30s', target: 0 },    // Ramp down
  ],
  
  // Thresholds (SLA)
  thresholds: {
    http_req_duration: ['p(95)<500'],  // 95% requests < 500ms
    http_req_failed: ['rate<0.01'],     // Error rate < 1%
  },
  
  // Load zones (distributed testing)
  ext: {
    loadimpact: {
      name: 'My Load Test',
      distribution: {
        'amazon:us:ashburn': { weight: 50 },
        'amazon:eu: Dublin': { weight: 50 },
      },
    },
  },
};