Symptoms, not causes
Alert on high error rates, slow responses and failed checkouts. CPU at 90% is not a problem if nobody is waiting; a checkout failing at 3% is a problem even at low CPU.
The three questions any dashboard should answer
Every monitoring setup should immediately answer:
- Is the site up right now
- Is it slower than usual
- Did anything change recently
Test the alerting path
Trigger a real alert quarterly. Alerting configurations decay: people leave, phone numbers change, and integrations expire silently.