Cagan describes telemetry/instrumentation as monitoring built into three layers — infrastructure, application, and user-experience — so a team can tell whether a deployment or a feature is actually working, not just that it shipped. Without it, teams are "flying blind": deployment success and feature success are different questions, and only instrumentation at all three levels answers both.
Telemetry underwrites the delivery-side claims teams need to make continuous delivery (Continuous Deployment Cadence) and release-risk techniques like Feature Flagging / Cohort Release credible — you can't dark-launch or A/B test a feature you haven't instrumented.
Part of the "how you build" axis of the Three-Axis Transformation Diagnostic (Build / Solve / Decide).
Из тем: The Product Operating Model