core practice · system design prompt
Define a north-star metric
Pick a product. Define its north-star metric (one number that captures customer value), 2-3 input metrics that drive it, and a guardrail metric you must not regress.
The mechanism
Good analytics looks like a small tree: one north-star metric that captures the value users get, two or three input metrics that drive it, and one guardrail you must not regress on. If a PM cannot make a tradeoff from this tree alone, the tree is wrong.
Expected evidence
A tree: north-star → inputs → guardrail, each with a one-sentence rationale.
Try this drill in the practice workspace →
Hints when you need them
- North-star is not revenue. It is the value the user gets.
- A good guardrail is something you would never trade away.