I built a free trading journal app as a solo developer — here's what I learned

#flutter #fintech #sideprojects #firebase

As a solo developer, I spent months building TraderTracking — a multi-asset trading journal and portfolio tracker for forex, crypto, and stock traders. Here's my journey and what I learned along the way.

Why I built it

I was tired of tracking my trades in spreadsheets. Existing tools were either too expensive, too complex, or didn't support multiple asset types in one place. So I decided to build my own.

The tech stack

Frontend: Flutter (single codebase for Android and Web)
Backend: Firebase (Auth, Firestore, Cloud Functions, Crashlytics, Analytics)
Ads: AdMob (native ads)
CI/CD: Custom build scripts with Dart obfuscation

Key features

Automatic P&L calculations (lot × pip × multiplier)
Multi-account support (track different brokers separately)
Live market prices for 50+ instruments
Built-in economic calendar
Customizable watchlists
Support for 13 languages
Works on Android and Web

Lessons learned

Start with the core problem. Don't build features nobody asked for. I focused on trade logging and P&L tracking first, then expanded.
Internationalization from day one. Adding 13 languages later would have been a nightmare. I built the i18n system early and it paid off.
Flutter is great for solo devs. One codebase for Android and Web saved me hundreds of hours.
Firebase scales well for indie projects. Auth, Firestore, and Cloud Functions handle everything I need without managing servers.
Ship early, iterate fast. My first version was rough, but real user feedback shaped the product into something much better.