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Kasa
Backend Software Engineer
Project Experience · Selected Work
A Bitfinex auto-lending platform I designed, built, and run myself. Pricing anchors to market depth; order placement is idempotent, with circuit breaking and full audit and monitoring. It started as a Python/FastAPI + Vue prototype, then I rewrote it end to end in Spring Boot + Next.js for stability and easier maintenance.
Key Responsibilities
- Sole full-stack owner: backend, frontend, database, deployment, and production ops
- Designed the market depth-anchored lending pricing strategy and order engine
- Built the reliability and security side: key encryption, audit logging, notifications, monitoring
- Set up containerized deployment and CI/CD so the service runs on its own
Technical Implementation
- Backend in Spring Boot 3 / Java 21: RESTful API with Spring Security JWT and TOTP two-factor auth
- Frontend in Next.js / React + Tailwind CSS + shadcn/ui, statically exported and deployed on Cloudflare Pages
- Lending engine runs on a scheduled cycle with periodic reconciliation, using a write-DB-before-order idempotent design to avoid duplicate placements
- Depth-anchored dynamic pricing against the funding order book, guarded by rate sanity checks
- Integrated Bitfinex REST v2 (HMAC-SHA384) protected by a Resilience4j circuit breaker and a Redis token-bucket rate limiter
- PostgreSQL (Flyway-versioned) + Redis (cache / distributed lock / rate limiting); user API keys stored AES-256 encrypted
- Email (Resend) and Telegram notifications for earnings digests and system alerts
- Tamper-evident audit log via a hash chain; monitoring and alerting with Prometheus + Grafana + Alertmanager
- Multi-stage Docker builds + Cloudflare Tunnel reverse proxy; GitHub Actions CI/CD with secrets managed in 1Password
Results & Impact
- The engine runs fully automated; idempotency and reconciliation mean no duplicate orders and a self-heal back to a consistent state when something fails
- Circuit breaking and rate limiting isolate exchange-side outages, so the service stays up when the exchange doesn't
- Structured logging with Prometheus/Grafana makes issues fast to pinpoint
- Grew from a one-person script into a layered, testable multi-module platform
Backend Engineer · Payments & Gaming Platform Integration
2023/10 - PresentOn the engineering team, integrating third-party payment gateways and gaming platforms and optimizing the backend, mainly to keep payments stable.
Key Responsibilities
- Developed and integrated third-party payment gateway APIs in Java Spring Boot
- Integrated gaming platforms and improved API efficiency and data sync
- Optimized the backend admin system for speed and stability
Technical Implementation
- Integrated several third-party payment APIs, reaching a 99.9% payment success rate
- Cut average backend request processing time by 30%
- Supported other teams, resolving issues quickly and improving product workflows
Results & Impact
- More stable payments and a better checkout experience
- Cut issue reports on payment and gaming interfaces by 50%
- Made the backend easier to maintain and scale
C# Engineer · POS & BI Systems
2022/09 - 2023/10C# engineer working on POS systems, the backend admin system, and BI reports, keeping things stable and improving them over time.
Key Responsibilities
- Built POS systems in C# and integrated various peripheral devices
- Built backend systems in .NET Core for scheduled tasks and data management
- Built BI reports to visualize data for decisions
- Maintained and improved existing systems, resolving user issues quickly
Technical Implementation
- Built scheduled-task modules that improved automated data processing
- Integrated BI tools and built 20+ report types for business decisions
- Kept existing systems running stably for over a year with the team
Results & Impact
- Made report queries 40% faster
- Cut POS issue reports by 30%
- Improved cross-team collaboration and noticeably sped up development