North Star- New-net-referrals-per-active-user-per-month (NNRPU): (# of successful referred users who convert to paying/active status within 30 days) ÷ (monthly active users). Focuses on referral program efficiency and reach per user.Supporting metrics- Referral conversion rate = referred_signups / referral_invitations_sent- Time-to-convert (median days from invite->activation)- Viral coefficient = avg invites sent per user * conversion rate- CAC for referred vs organic- Revenue lift from referrals (LTV_referred / LTV_nonreferred)- Cohort retention: 7/30/90-day retention for referred vs baseline- Promo utilization and incrementality (A/B lift vs control)Instrumentation events (sample schema)- referral_invite_sentjson
{
"event":"referral_invite_sent",
"user_id":"string",
"invite_id":"string",
"channel":"email|sms|link|social",
"recipient_contact":"hash_or_domain",
"timestamp":"iso8601",
"campaign_id":"string|null",
"device":"ios|android|web",
"metadata":{}
}
- referral_clickjson
{
"event":"referral_click",
"invite_id":"string",
"click_id":"string",
"referrer_user_id":"string",
"timestamp":"iso8601",
"utm":{"source","medium","campaign"},
"ip_hash":"string"
}
- referral_signupjson
{
"event":"referral_signup",
"signup_id":"string",
"invite_id":"string|null",
"referrer_user_id":"string|null",
"new_user_id":"string",
"timestamp":"iso8601",
"attribution_window_days":30
}
- referral_conversionjson
{
"event":"referral_conversion",
"new_user_id":"string",
"referrer_user_id":"string|null",
"invite_id":"string|null",
"conversion_type":"paid|activated",
"amount":"decimal|null",
"timestamp":"iso8601"
}
Attribution logic- Use invite_id primary key; fallback to click_id + ip_hash + device fingerprint; enforce 30-day attribution window; record multi-touch if multiple invites.Guardrails to detect fraud / side effects- Rate limits: flag users sending > X invites/day or per-recipient frequency- Unusual patterns: spike detection on invites/clicks from single IP/IP subnet, same device_id or same recipient_contact hashed across many referrers- Conversion anomalies: unusually high conversion rates (>99%) or extremely fast conversions (<1 minute) flagged- Cohort sanity checks: compare LTV/retention of referred cohorts vs organic; if referred LTV << organic, check for abuse- Duplicate/new user churn: monitor % of referred signups that are churned/delete within 7 days- Financial guardrail: total projected referral payouts vs budgeted cap; throttle program if > threshold- Manual review queue: auto-flagged invites/conversions routed for human reviewImplementation notes / OKRs- Instrument all events with consistent user and invite IDs; ensure idempotency keys- Build dashboards: real-time invite funnel, cohort retention, fraud alerts, ROI (LTV vs payout)- OKR example: Increase NNRPU by 25% in Q1 while keeping fraudulent conversions <1% and payout ROI >3x LTV/payout ratio.This framework supports operational reporting, cohort analysis, A/B lift measurement, and automated fraud detection suited for BI-driven decision making.