The ELO Score

Early apps ranked users by "desirability". If a popular person swipes right on you, your score goes up. Modern apps use vectors of taste.

Preferences vs Behavior

Users say they want "Kind, 6ft tall". They swipe on "Hot, Bad Boy". Algorithms trust behavior (swipes) over stated preferences.

Location Geohashing

Use Geohash or S2 cells for efficient "people near me" queries. Calculate radius search on grid cells, not raw coords.

The Stability/Retention Paradox

A perfect match means two users leave the app (churn). Apps must balance successful matches with keeping users swiping.

Cold Start Problem

New users need exposure to get a "score". Boost new profiles temporarily to gather data and hook them with matches.

Safety and Spam

Detect bots early. Verify photos with selfie-challenges (pose matching). Block device IDs of banned predators.

Monetizing Desperation

Super Likes and Boosts work because they bypass the black-box algorithm. Selling "visibility" is the core business model.