Define and measure product–market fit (PMF) for Alexa Shopping. Propose a metric framework including activation (first successful purchase via voice with payment set up), engagement (weekly voice shopping intents per active household, voice-share of total Amazon purchases), retention (W1, W4, W12 household retention on any voice shopping action), and satisfaction (PMF survey: % extremely disappointed if removed; task success rate). Specify event instrumentation, household vs device identity, cohorting rules (by first activation month), seasonality controls (prime day/holidays), and leading indicators (repeat purchase intent, saved reorder lists). Design how you’d set PMF thresholds, run longitudinal cohort analysis, and reconcile conflicting signals (e.g., high survey PMF but low repeat). Include a plan to validate causality of PMF drivers (e.g., intent understanding improvements) via experiments or causal inference.