CoinTopper
Real-time crypto prices on mid-range phones and patchy networks.
The tension
Crypto prices never stop moving, but the phones and networks of many users couldn’t keep up with a firehose of updates.
- Role
- Software Engineer · Sep 2017 — Dec 2018
- What I owned
- Built the CoinTopper Android app at CodeCrunch, alongside the company’s other flagship product, Studentdesk.in.
- Platforms
- Android
- Links
- Website
- prices, volume & charts
- Live
- daily active users handled
- 10K+
Context
CoinTopper tracks cryptocurrency markets in real time — prices, volume, live charts and more. I built its Android app as one of CodeCrunch’s flagship products, during the 2017–18 crypto boom.
Engineering nuance
1. Streams, not refresh buttons
Constraint. Prices change constantly; the UI had to stay smooth while updates kept arriving.
Decision. A reactive data layer with RxKotlin, streaming updates into the UI off the main thread.
Trade-off. Rx has a steep learning curve, but it made throttling and combining data streams straightforward.
2. Show something instantly
Constraint. On slow networks, an empty list while prices load feels broken.
Decision. Persist watchlists and recent market data locally with DBFlow, so the app opens on the last known state and refreshes in place.
3. Testable by default
Constraint. Market data is messy, and bugs in numbers destroy trust.
Decision. An MVP architecture with Dagger2 dependency injection and a test-driven approach, so logic could be tested away from Android.
Outcome
- Part of a product suite that handled 10,000+ daily active users.
- A polished Material Design app with real-time charts and Lottie animation.
