Define and critique a user activity metric

## Context You are on a product team and need to define a metric for **user activity** to be used in dashboards and decision-making. ## Question 1. Propose **2–4 candidate definitions** of “active user” (e.g., DAU/WAU/MAU), including the exact event logic (what counts as activity). 2. For each definition, discuss: - pros/cons and what product behavior it captures - sensitivity to spam/bots, accidental opens, and background activity - how it behaves with different product usage patterns (daily vs occasional) - how time windowing/timezone choices affect the metric 3. Recommend a **primary metric** plus **diagnostic and guardrail metrics** you would pair with it, and explain why. Assume you have event logs with at least: `user_id`, `event_name`, `event_time` (UTC), `platform`, and relevant event properties.