Synthetic monitoring
Synthetic monitoring runs scripted, simulated user transactions against a production service from external locations on a fixed cadence, typically every 1-5 minutes from multiple geographies. Unlike real-user monitoring, synthetic checks run regardless of actual traffic, so they detect availability gaps during low-traffic periods and verify the full user flow end-to-end.
Common synthetic check types: simple availability ping (HTTP GET expecting 200), full transaction flow (login → search → add-to-cart → checkout), API contract check (POST a known payload, assert response schema), and DNS/CDN/SSL check (verify the edge layers haven't broken). Tools include Datadog Synthetics, Grafana Synthetic Monitoring, Pingdom, StatusCake. The trade-off vs real-user monitoring: synthetic catches outages even with zero real users (useful at night), but it can miss failure modes that only specific user paths trigger. Healthy practice runs both, synthetic for availability SLO, real-user for performance SLO.