How to Set Up Synthetic Monitoring for Critical User Journeys

Synthetic monitoring proactively tests your application by simulating real user actions on a schedule — catching issues before actual users encounter them, rather than only learning about problems reactively.

Synthetic Monitoring vs Real User Monitoring

Synthetic monitoring runs scripted checks continuously regardless of actual traffic; real user monitoring (RUM) observes genuine user sessions — synthetic monitoring catches issues even during low-traffic periods when RUM might not surface a problem quickly.

What to Monitor Synthetically

Critical business flows: login, checkout, core feature usage
Key API endpoints your application depends on
Anything where a silent failure would have significant business impact

Prerequisites

A tool capable of scripted browser automation (e.g. Playwright or Puppeteer)

Step 1 — Install a Browser Automation Tool

npm install playwright
npx playwright install

Step 2 — Write a Synthetic Test for a Critical Journey

const { chromium } = require('playwright');

async function testLoginFlow() {
  const browser = await chromium.launch();
  const page = await browser.newPage();

  await page.goto('https://yourapp.com/login');
  await page.fill('#email', '[email protected]');
  await page.fill('#password', 'TEST_PASSWORD');
  await page.click('#login-button');

  await page.waitForSelector('#dashboard', { timeout: 10000 });
  console.log('Login flow: SUCCESS');

  await browser.close();
}

testLoginFlow().catch((err) => {
  console.error('Login flow: FAILED', err);
  process.exit(1);
});

Step 3 — Use a Dedicated Test Account

Never run synthetic tests against real customer accounts — create dedicated test accounts specifically for monitoring purposes, isolated from production customer data.

Step 4 — Run on a Schedule

crontab -e

*/5 * * * * /usr/bin/node /path/to/synthetic-test.js >> /var/log/synthetic-tests.log 2>&1

Step 5 — Alert on Failures

node synthetic-test.js || curl -X POST YOUR_ALERTING_WEBHOOK -d "Login flow synthetic test failed"

Integrate with your existing alerting system (see How to Set Up Effective Server Alerting) so a failed synthetic test triggers the same escalation path as other critical alerts.

Testing from Multiple Locations

For geographically distributed audiences, running synthetic tests from multiple regions can catch region-specific issues (CDN problems, regional network routing issues) that a single-location test would miss.

Measuring Performance, Not Just Success/Failure

const startTime = Date.now();
await page.goto('https://yourapp.com/login');
const loadTime = Date.now() - startTime;

if (loadTime > 3000) {
  console.warn(`Slow page load: ${loadTime}ms`);
}

Track timing alongside pass/fail status, feeding this into your metrics system for trend visibility over time, not just point-in-time pass/fail checks.

Keeping Synthetic Tests Maintained

UI changes can break synthetic tests even when the underlying functionality is fine — review and update test scripts when the application's UI changes, treating them as living code requiring maintenance, not "write once" scripts.

Common Errors

Test fails intermittently with no clear pattern — consider adding more generous wait conditions/timeouts for elements to load, since flaky synthetic tests undermine trust in genuine failure alerts.

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