🟠Product Sense: Metric Design
North Star metrics (memorize a few)
| Company | North Star |
|---|---|
| Daily active users | |
| Airbnb | Nights booked |
| Spotify | Time spent listening |
| Slack | Messages sent per user per day |
| Uber | Rides completed |
The counter-metric test
For ANY proposed metric, ask: "What happens if someone games this?" - "Clicks" → people click but immediately bounce (meaningless) - "Time spent" → people are frustrated and can't find what they need - "Messages sent" → spam bots inflate numbers
This is why you need guardrail metrics — they catch when a win on one dimension creates a loss elsewhere.
Vanity vs actionable metrics
Vanity: total registered users, total page views, total downloads. Only go up. Tell you nothing about health.
Actionable: DAU/MAU ratio (stickiness), retention rate (d1/d7/d30), revenue per user, conversion rate.
Practice Questions
Q: "Total app downloads reached 50 million!" Is this a good success metric?