Harbor Pay

The challenge

Harbor Financial was moving off a third-party processor. Every payment had to be correct to the cent, even when networks failed halfway through.

What I built

I designed a payments API in Kotlin with idempotent requests, an event-sourced ledger on PostgreSQL, and automated reconciliation that runs every hour.

The result

Harbor now processes 1.5M payments a month at 99.99% uptime, with zero double charges since launch and settlement times cut from three days to one.