2026Full-stack developmentReady
Paywall
A wallet and merchant checkout platform, built to get the money-handling parts right.
Overview
Paywall is a two-sided payments build. Customers hold a wallet, top it up through simulated bank pages, and send money to each other by phone number. Merchants create payment links, collect from a wallet at checkout, and review customers, payments, and settlements.
It is a Turborepo of three apps — the customer wallet, the merchant workspace, and an Express webhook service — sharing one Prisma schema on PostgreSQL. No real bank, card, or payout is involved; the point of the project is the correctness of the balance handling underneath.
Highlights
- Every balance change runs inside a PostgreSQL transaction with SELECT ... FOR UPDATE row locks, so concurrent debits cannot race.
- Amounts stored as integer paise rather than floats, so rounding drift never accumulates.
- Nine-model schema covering wallets, transfers, payment links, merchant customers, payments, and settlements.