So far all observability pointed inward—CPU, memory, error rates, cold starts. Yet every metric green while users complain "site is slow." Specific CDN edge slow, JavaScript breaks in certain browser, DNS hiccups in region, backend fast but frontend render slow—possible. System metrics show "server healthy" but not "user actually experiences quality." Today: bridging that gap.
Three tools measuring user experience deep-dive. Synthetics (external simulation traffic active measurement), RUM (real browser passive collection), Evidently (compare two variants A/B test)