A product I architected, built, marketed and still support - alone.

Serbian flat-rate taxpayers run their businesses out of spreadsheets, PDFs and a shoebox. svezapausal.rs puts invoicing, KPO books, payment limits and tax obligations in one place, with ten free calculators and generators for people who reasonably will not pay for something until it has already helped them.

I first ran into how badly this is served at SymOrg 2018, a case competition where flat-rate taxation was the problem posed and my team took first place. The product is a separate and much later piece of work - the competition is where I learned the domain, not where the business came from.

Every part of it is mine: the architecture, the code, the pricing, the marketing and the support inbox. It is the clearest evidence that the product work I sell is not theoretical - it has paying customers and an operations burden I carry myself.