Performance Engineering

// load_tests/api_performance.js
import http from 'k6/http';
import { check, sleep } from 'k6';
import { Rate, Trend } from 'k6/metrics';

// Custom metrics
const errorRate = new Rate('errors');
const valuationLatency = new Trend('valuation_latency');

export const options = {
  scenarios: {
    // Baseline load
    constant_load: {
      executor: 'constant-vus',
      vus: 50,
      duration: '5m',
    },
    // Stress test
    stress: {
      executor: 'ramping-vus',
      startVUs: 0,
      stages: [
        { duration: '2m', target: 100 },
        { duration: '5m', target: 100 },
        { duration: '2m', target: 200 },
        { duration: '5m', target: 200 },
        { duration: '2m', target: 0 },
      ],
    },
    // Spike test
    spike: {
      executor: 'ramping-vus',
      startVUs: 0,
      startTime: '12m',
      stages: [
        { duration: '10s', target: 500 },
        { duration: '1m', target: 500 },
        { duration: '10s', target: 0 },
      ],
    },
  },
  thresholds: {
    http_req_duration: ['p(95)<200', 'p(99)<500'],
    errors: ['rate<0.01'],
    valuation_latency: ['p(95)<300'],
  },
};

export default function () {
  // Valuation endpoint test
  const productId = `prd_${Math.random().toString(36).substr(2, 9)}`;
  const start = Date.now();
  
  const res = http.get(
    `${__ENV.API_URL}/api/v1/valuations/${productId}`,
    {
      headers: { 'Authorization': `Bearer ${__ENV.API_KEY}` },
    }
  );
  
  valuationLatency.add(Date.now() - start);
  
  const success = check(res, {
    'status is 200': (r) => r.status === 200,
    'latency < 500ms': (r) => r.timings.duration < 500,
    'has valuation': (r) => JSON.parse(r.body).valuation !== undefined,
  });
  
  errorRate.add(!success);
  sleep(1);
}