DBKZ · Contract · Sep 2024 — Present
Medical billing across 74 hospitals
End-to-end billing product for a medical operation moving about R$1.5M every month.
The idea
Billing here is not a checkout. It is matching tens of thousands of payment rules to procedure codes so hospitals can issue boletos every month—without a second engineer on the product.
The situation
The operation moves about R$1.5M a month across 74 hospitals. The product had to own the full path: which rule applies, which procedure is being billed, how the boleto goes out, and how the hospital is told.
I was the only engineer on that surface. System design, cloud layout, and the SQL model all sat in the same place as the apps people actually used.
How it works
Treat billing as a rules engine with a human surface, not as a form that dumps into a spreadsheet. Twenty-five thousand payment parameters and four thousand procedures have to resolve into one payable document. If that match is wrong, the month does not close.
The work was to make that match boring: model it in SQL, expose it through a NestJS API, and give operators a Next.js console and a React Native app that talk to the same contract.
What shipped
The API, the mobile app, and the web app went out together. Boleto, email, WhatsApp, uploads, and analytics were wired into the same flow so a billed procedure did not die in a side channel.
- 01Resolve payment parameters25,000 rules
- 02Match procedure codes4,000 procedures
- 03Issue boleto & notifyemail + WhatsApp
- Hospitals
- 74
- Monthly
- R$ 1.5M
- Surfaces
- 3
The problem
Own system design, cloud layout, and SQL modeling for 25,000 payment parameters and 4,000 procedures—without a second engineer on the product.
What shipped
Shipped the NestJS API, React Native app, and Next.js web app, and wired boleto payments, email, WhatsApp, uploads, and analytics.