---

name: load-test-scenario-builder description: Creates comprehensive load test plans with realistic scenarios, traffic models, k6 scripts, and success criteria. Use for "load testing", "performance testing", "capacity validation", or "stress testing".

Load Test Scenario Builder

Validate system capacity with realistic load tests.

Load Test Scenarios

Copyinterface LoadTestScenario {
  name: string;
  description: string;
  virtualUsers: number;
  duration: string;
  rampUp: string;
  successCriteria: {
    p95Latency: number;
    errorRate: number;
    throughput: number;
  };
}

const scenarios: LoadTestScenario[] = [
  {
    name: "Baseline Load",
    description: "Normal traffic pattern",
    virtualUsers: 100,
    duration: "10m",
    rampUp: "2m",
    successCriteria: {
      p95Latency: 500, // ms
      errorRate: 0.01, // 1%
      throughput: 1000, // req/s
    },
  },
  {
    name: "Peak Load",
    description: "Black Friday traffic",
    virtualUsers: 1000,
    duration: "30m",
    rampUp: "5m",
    successCriteria: {
      p95Latency: 2000,
      errorRate: 0.05,
      throughput: 5000,
    },
  },
  {
    name: "Stress Test",
    description: "Find breaking point",
    virtualUsers: 5000,
    duration: "20m",
    rampUp: "10m",
    successCriteria: {
      p95Latency: 5000,
      errorRate: 0.1,
      throughput: 10000,
    },
  },
];

K6 Load Test Script

Copy// load-tests/checkout-flow.js
import http from "k6/http";
import { check, sleep } from "k6";
import { Rate } from "k6/metrics";

const errorRate = new Rate("errors");

export let options = {
  stages: [
    { duration: "2m", target: 100 }, // Ramp up
    { duration: "10m", target: 100 }, // Stay at 100
    { duration: "2m", target: 0 }, // Ramp down
  ],
  thresholds: {
    http_req_duration: ["p(95)<500"], // 95% under 500ms
    errors: ["rate<0.01"], // Error rate <1%
  },
};

export default function () {
  // 1. Browse products
  let browseRes = http.get("https://api.example.com/products");
  check(browseRes, {
    "browse status 200": (r) => r.status === 200,
  }) || errorRate.add(1);
  sleep(1);

  // 2. Add to cart
  let addCartRes = http.post(
    "https://api.example.com/cart",
    JSON.stringify({
      productId: "123",
      quantity: 1,
    }),
    {
      headers: { "Content-Type": "application/json" },
    }
  );
  check(addCartRes, {
    "add cart status 201": (r) => r.status === 201,
  }) || errorRate.add(1);
  sleep(2);

  // 3. Checkout
  let checkoutRes = http.post(
    "https://api.example.com/checkout",
    JSON.stringify({
      paymentMethod: "card",
    }),
    {
      headers: { "Content-Type": "application/json" },
    }
  );
  check(checkoutRes, {
    "checkout status 200": (r) => r.status === 200,
    "checkout success": (r) => r.json("status") === "success",
  }) || errorRate.add(1);
  sleep(3);
}

Traffic Models

Copy// Realistic traffic patterns
export const trafficModels = {
  // Steady state
  steadyState: {
    stages: [{ duration: "30m", target: 500 }],
  },

  // Gradual ramp
  gradualRamp: {
    stages: [
      { duration: "5m", target: 100 },
      { duration: "5m", target: 300 },
      { duration: "5m", target: 500 },
      { duration: "10m", target: 500 },
      { duration: "5m", target: 0 },
    ],
  },

  // Spike test
  spikeTest: {
    stages: [
      { duration: "2m", target: 100 },
      { duration: "1m", target: 2000 }, // Sudden spike
      { duration: "2m", target: 100 },
    ],
  },

  // Soak test (endurance)
  soakTest: {
    stages: [
      { duration: "5m", target: 500 },
      { duration: "4h", target: 500 }, // Long duration
      { duration: "5m", target: 0 },
    ],
  },
};

Success Thresholds

Copyexport const thresholds = {
  // Latency
  http_req_duration: [
    "p(50)<200", // 50% under 200ms
    "p(95)<500", // 95% under 500ms
    "p(99)<1000", // 99% under 1s
  ],

  // Error rate
  http_req_failed: ["rate<0.01"], // <1% errors

  // Throughput
  http_reqs: ["rate>1000"], // >1000 req/s

  // Custom metrics
  checkout_duration: ["p(95)<2000"],
  checkout_success_rate: ["rate>0.95"],
};

Running Load Tests

Copy#!/bin/bash
# scripts/run-load-tests.sh

echo "Running load tests..."

# Baseline test
k6 run --vus 100 --duration 10m load-tests/checkout-flow.js

# Peak load test
k6 run --vus 1000 --duration 30m load-tests/checkout-flow.js

# Stress test (find breaking point)
k6 run --vus 5000 --duration 20m load-tests/stress-test.js

# Generate report
k6 run --out json=results.json load-tests/checkout-flow.js
k6 run --out influxdb=http://localhost:8086 load-tests/checkout-flow.js

Result Analysis

Copyinterface LoadTestResult {
  scenario: string;
  timestamp: Date;
  metrics: {
    p50Latency: number;
    p95Latency: number;
    p99Latency: number;
    errorRate: number;
    throughput: number;
    maxVUs: number;
  };
  passed: boolean;
  notes: string[];
}

function analyzeResults(results: LoadTestResult) {
  console.log(\`Load Test: \${results.scenario}\`);
  console.log(\`Status: \${results.passed ? '✅ PASS' : '❌ FAIL'}\`);
  console.log(\`p95 Latency: \${results.metrics.p95Latency}ms\`);
  console.log(\`Error Rate: \${(results.metrics.errorRate * 100).toFixed(2)}%\`);
  console.log(\`Throughput: \${results.metrics.throughput} req/s\`);

  if (!results.passed) {
    console.log('Failed criteria:');
    results.notes.forEach(note => console.log(\`  - \${note}\`));
  }
}

Output Checklist

• Scenarios defined
• k6 scripts created
• Traffic models configured
• Success criteria set
• CI integration
• Results analysis ENDFILE