A developer has shared “Loyalty Ledger,” a prototype fan loyalty tracker that records check-in streaks, badge tiers, and related history on Solana rather than in the app’s own database. The project targets a common issue in sports apps: streaks and loyalty history can reset when users stop using an app, switch services, get banned, or when the service deletes inactive accounts. In this build, a user connects a crypto wallet, selects a sport and team, and performs a “check-in” that sends an actual on-chain transaction. For FIFA World Cup, the app writes to a Solana program-owned account, updating streak counts and timestamps and supporting badge claims. The developer describes the core data structure as a small Anchor program that assigns each fan a PDA (program-derived address) keyed to the wallet, sport, and team, while storing streak-related fields and also keeping sport and team as explicit account fields to enable leaderboard queries. The interface includes a Fan Passport, derived “Fan Score,” achievement views, and a leaderboard based on on-chain state. The app uses Solana Devnet for testing, and developers can mint an SPL token badge after crossing a tier threshold; other sports mentioned in the UI are described as stubbed or sample-based.