Observability
Real User Monitoring vs Synthetic Checks for Uptime
Combine synthetic and RUM to see outages the same way customers do.
By Jordan LeePublished November 15, 20255 min read
When synthetic wins
Synthetic checks find cold start, DNS, and TLS issues before users notice.
They also provide clean baselines for SLO tracking.
If synthetic checks fail but RUM is calm, you likely broke auth or routing before users hit it.
When RUM is irreplaceable
RUM exposes device, browser, and ISP differences synthetic probes cannot mimic.
It surfaces frustration signals like rage clicks when latency creeps up.
Blend signals
- Use synthetic to guard dependencies
- Use RUM to validate user experience
- Alert when both spike to avoid noise
How to wire both in Watch.Dog
Pair each synthetic monitor with a RUM widget on the same dashboard.
Link alerts to the same incident so owners see both traces and steps.