Recova: B2B payment collections platform

The problem: late B2B payments tie up working capital for small businesses. Finance teams chase customers by hand and reconcile gateway payouts against spreadsheets, where one missed or double-counted payment is expensive.

What I built: a multi-tenant accounts-receivable platform for Indian SMEs. It issues GST invoices, shares payment links, sends automated reminders, takes gateway payments through signed webhooks and reconciles every rupee. There is a Next.js dashboard on top of a Java backend.

The parts that matter with money: login with rotating refresh tokens, a transactional outbox to Kafka with idempotent consumers so no payment event is lost or processed twice, signed webhook verification, and resilience patterns around the gateway calls.

How I tested it: 60 backend tests using real PostgreSQL, Redis and Kafka in containers, plus browser tests of the dashboard. A k6 load test on one laptop processed about 687 payments per second at a p95 of 21 ms with zero errors, and the reconciliation check afterwards found 0 mismatches across 20,859 payments.

Important: the payment gateway and the email and SMS channels are mocks. No real money or messages move. Stack: Java 21, Spring Boot 3.5, PostgreSQL, Kafka, Redis, Next.js 16. This is a personal project. Code is on my GitHub: chaitanya-mhetre, repository payment-collections-platform.