Supplement Ordering with a Double-Entry Ledger
What it does
A provider builds a supplement order for a patient, and the patient pays through a pay link (payments are faked). On payment, one database transaction splits the total into cost of goods, the provider’s payout and a 75 bps platform fee, recorded as balanced double-entry ledger rows. An audit page shows where every cent of a paid order went.
Claude also turns a protocol note into a suggested order, constrained by a strict schema with a keyword fallback. Refunds post reversing entries, and orders can be reordered or cancelled.
- Provider builds orderfrom catalog prices
- Patient payspay link, faked payments
- One transactionserver recomputes the split
- Ledger entriesCOGS, payout, 75 bps fee
- Refundsreversing entries, never edits
Engineering notes
Money is integer cents everywhere, ledger rows are append-only, and the server recomputes every split instead of trusting the client. It’s tested with property tests and a red-team suite.
Tools
TypeScript, Fastify, Vue 3, Drizzle, Postgres, Vitest, fast-check, Playwright, Claude Haiku, Render