Overview
As a co-founder of Sireto Technology, I led the front-end and mobile development of a fintech platform adopted by financial institutions in Germany and the Netherlands for government-backed digital currency transactions. The platform handled real money movement in a regulated European context — which meant the engineering bar for correctness, uptime, and security was non-negotiable.
What I Built
Cross-Platform Client (ReactJS + React Native)
A single codebase serving both web and mobile clients — built in React Native for iOS/Android and ReactJS for the browser dashboard. The UI handled:
- Digital currency wallet management and transaction history
- Multi-step transfer flows with regulatory confirmation steps
- Real-time balance and transaction status feeds via WebSocket
- Localization for German and Dutch markets
Microservices Architecture
Integrated a full microservices backend spanning:
- Authentication — JWT with refresh token rotation, 2FA
- Payment Services — transaction initiation, validation, settlement
- Ethereum/Bitcoin Nodes — on-chain transaction broadcasting and confirmation monitoring
- Media Storage — document uploads for KYC verification flows
- Email/Messaging — transactional notifications and compliance alerts
All services containerized with Docker; CI/CD via GitHub Actions with automated test gates before any production deploy.
Distributed P2P Backend (Kademlia)
For node discovery within the network, I built a distributed P2P backend in Java implementing the Kademlia DHT protocol — the same algorithm underlying BitTorrent and Ethereum’s devp2p layer. This enabled resilient peer discovery without a central coordinator.
Smart Contract Layer
Developed reusable ERC-20 CRUD smart contracts in Solidity and integrated them with the Java backend. I also researched known Solidity vulnerability patterns (reentrancy, integer overflow, front-running) to harden contracts before deployment.
Database Optimization
Designed the SQLite schema for the mobile client with normalization, strategic indexing, and a sync mechanism for offline-capable operation. Performance improved 250% over the initial naive schema.
Stack
ReactJS · React Native · Java · Solidity · Ethereum · ERC-20 · Kademlia DHT · Docker · CI/CD · SQLite · REST APIs