Synthetic monitoring (Lighthouse CI, automated browser tests) catches regressions in controlled conditions. RUM (Real User Monitoring) captures what actually happens across your user base — different devices, networks, geographies, and browser versions. ISO 25010:2011 time-behaviour requires measuring real performance; without RUM, you are optimizing against lab conditions that may not match production. Without synthetic monitoring, you lack a baseline to detect regressions before they affect users.
Low because monitoring is detective rather than preventive — its absence does not degrade performance directly, but means regressions go undetected until user complaints surface them, often after significant impact.
Integrate the web-vitals library to collect LCP, CLS, and FID/INP from real users and send to your analytics backend. Pair with Lighthouse CI for synthetic baselines.
// app/layout.tsx — report Web Vitals to your analytics endpoint
import { useReportWebVitals } from 'next/web-vitals'
export function WebVitalsReporter() {
useReportWebVitals((metric) => {
fetch('/api/vitals', {
method: 'POST',
body: JSON.stringify({ name: metric.name, value: metric.value, id: metric.id }),
})
})
return null
}
ID: performance-deep-dive.regression-prevention.rum-synthetic-monitoring
Severity: low
What to look for: Count all monitoring integrations. Enumerate which provide RUM (Real User Monitoring) vs. synthetic monitoring. At least 2 monitoring types needed. Look for monitoring service integrations (web-vitals, Sentry, Datadog, New Relic, Google Analytics 4). Check for RUM (Real User Monitoring) dashboards. Look for synthetic monitoring (Lighthouse CI, Browserstack, etc.).
Pass criteria: Both RUM and synthetic monitoring are configured. RUM captures real user metrics (LCP, CLS, FID). Synthetic monitoring runs automated tests on each deploy.
Fail criteria: No monitoring configured, or only one type (RUM or synthetic, not both).
Skip (N/A) when: Never — monitoring is essential for production applications.
Cross-reference: For regression alerts built on monitoring data, see regression-alerts-configured.
Detail on fail: "No monitoring configured — performance regressions undetected until users complain" or "Only synthetic monitoring; no real user data about actual performance"
Remediation: Integrate web-vitals and a monitoring service like Sentry, Datadog, or New Relic.
// app/layout.tsx — web-vitals RUM integration
import { useReportWebVitals } from 'next/web-vitals'
useReportWebVitals((metric) => fetch('/api/vitals', { method: 'POST', body: JSON.stringify(metric) }))