ProxxlyOffline-capable tap payments infrastructure

Every contactless payment system in Ghana needs special hardware most small merchants can't afford, while the NFC chip already in everyone's phone sits unused.

Connectivity is also least reliable exactly where small payments happen — trotro stops, market interiors, campus corners.

An Android SDK and REST API built on a multi-tenant, double-entry ledger. One phone emulates a contactless card; another reads it like a terminal. No special hardware on either side.

The tap completes entirely offline — the two phones authenticate each other cryptographically — and settles later once a connection returns.

It's not a consumer wallet app; it's infrastructure other products (banks, transport operators, schools, apps) integrate with, the way a shopper never sees Paystack directly.

• 212 automated tests passing
• 10,000 concurrent ledger operations with zero reconciliation drift
• 50 offline taps settled exactly once, end-to-end, on reconnect
• The offline protocol is independently implemented twice, in TypeScript and Kotlin, locked to shared test vectors so the two can't silently drift
• The ledger is append-only, enforced at the database level

Proxxly is pre-pilot: no pilot exists yet and no real money has moved through the system. It is designed for Ghana's regulatory environment, with a closed-loop-first approach.

• Kotlin / Android
• Host Card Emulation
• NFC reader mode
• Hardware-backed Keystore
• TypeScript
• Fastify
• PostgreSQL
• ECDSA P-256
• AES-256-GCM