Metrics & North Star

North Star Metric (NSM)

Sean Ellis: "One metric that best captures the core value your product delivers." NSM đáp ứng 3 tiêu chí:

1. Reflect user value (không phải vanity).
2. Measurable accurately, frequently.
3. Actionable — team có thể tác động trực tiếp.

Ví dụ NSM

Metric hierarchy

• North Star — 1 metric.
• L1 input metrics — 3–5 driver của NSM (acquisition, activation, retention, revenue).
• L2 feature metrics — đo từng feature individual.
• Guardrails — không được giảm (latency, NPS, error rate).

Leading vs Lagging

• Lagging — revenue, churn (đo sau).
• Leading — engagement signal predict revenue/churn (đo trước).

Goodhart's Law

"When a measure becomes a target, it ceases to be a good measure." Ví dụ: target DAU → team push notification spam → DAU tăng nhưng retention long-term giảm. Counter bằng guardrail metric.

Common pitfalls

• Vanity metric — page view, signup không reflect value.
• Quá nhiều NSM — defeats the purpose.
• NSM = revenue — lead to short-term hack.
• Không define "active user" rõ → confusion ở weekly review.

Vietnam context

E-commerce VN: tránh dùng GMV làm NSM (có thể game bằng coupon). Dùng "delivered orders" hoặc "repeat customers". Edtech: lessons completed thay vì signups.