BNPL Platform

Overview

A full-stack Buy Now, Pay Later (BNPL) microservices platform modeled after services like Sezzle. Three independently deployed Go services backed by a React/TypeScript merchant dashboard, all orchestrated with Docker Compose. The BNPL Engine handles order creation and installment payment processing. Money is stored as integers (cents) — never floats — to avoid IEEE 754 rounding errors. Payment splitting guarantees the sum always equals the original total: remainder cents are distributed to the earliest installments. SELECT FOR UPDATE row locks prevent double-payment race conditions under concurrent load. The service ships with 24 tests across unit, integration (real Postgres), and full HTTP end-to-end layers. The Merchant API adds JWT authentication, Elasticsearch-powered transaction search, and Postgres aggregate stats. The React dashboard surfaces these through debounced search, paginated transaction tables, an installment timeline per order, and protected routes — JWT stored in memory, never localStorage, to avoid XSS exposure.