yarn add Austin 😎💥

4 weeks ago, I started building Fastpay, a fintech mobile app, in public. I’ve worked on fintech applications for companies before, so the idea of building another fintech app wasn’t because I wanted to learn what a wallet, card, or transfer flow looks like. I wanted something I could put in my portfolio that actually shows how I approach building a complete fintech product, from the mobile interface to the backend systems behind it. So I started Fastpay from scratch. The first few days were mostly about getting the foundation right: setting up the Flutter application, authentication, OTP verification, PIN sign-in, and the Go + Gin + PostgreSQL backend. Then the project started becoming much more interesting. I began building the actual financial flows one by one, though I focused on internal wallet infrastructure and mocked external payments: sending and requesting money, deposits, QR payments, cards, transactions, currency exchange, IBAN and SWIFT transfers, phone top-ups, and scheduled transfers. And with every feature, I had to think beyond the screen. How should the API handle the transaction? What happens if a request is sent twice? What data should the backend store? How should the mobile app respond to different states? How should authentication and authorization be handled? At the same time, I paid a lot of attention to the UX. I wanted Fastpay to feel better to use, not just function correctly. I spent time simplifying flows, reducing unnecessary steps, improving how information is presented, and making different parts of the app feel consistent. That has probably been one of the most valuable parts of building Fastpay: taking the fintech patterns I’ve already experienced and rethinking how I would design and build them myself. I’ve also built the less visible parts of the product: analytics, notifications, security and privacy settings, device and session history, personal details, notification preferences, language settings and other account management flows. I’ve been sharing the process almost every day for the last 4 weeks, documenting how the product has evolved feature by feature. Fastpay is still a portfolio project, and I’m not building it with the intention of launching it as a fintech company. I’m building it to push my engineering skills, experiment with different approaches, and have a project that represents the kind of software I’m capable of building, both technically and from a UX perspective. I’m wrapping up the Fastpay build this week, and I’m looking forward to sharing the final result and everything that went into building it. I’m Ahiakwo John, a fullstack web and mobile app developer with over 4 years of experience, passionate about using technology and AI to build useful products. I’m open to collaboration and opportunities.