What is synthetic monitoring vs passive monitoring?
Answer
Synthetic monitoring (active monitoring): regularly executes pre-scripted transactions against your application to verify it's working — simulating user behavior proactively. Examples: ping a login endpoint every minute, run a checkout flow every 5 minutes. Detects issues before real users do. Tools: Datadog Synthetics, New Relic Synthetics, Pingdom, Checkly. Use for: SLA monitoring, uptime checks, critical user journey verification post-deployment. Passive monitoring (Real User Monitoring — RUM): observes actual user traffic and measures performance from real interactions — no synthetic traffic. Tools: Datadog RUM, Sentry Performance, Dynatrace, Google Analytics. Use for: understanding real user experience, identifying performance issues by geography or device. Combination: synthetic for proactive alerting (before users notice), passive for understanding real impact. In the testing context, synthetic monitoring is often called "production testing" or "testing in production" — running a subset of E2E tests against real production as smoke tests after deployment. Canary deployments combine monitoring with gradual rollout.