Open to opportunities

James Han

@jameshan

Message

Independent software engineer building end-to-end backend and native Apple apps with production LLM features.

United States

Message

What I'm looking for

I want to build and ship end-to-end products—especially backend services and native Apple apps—with production-quality engineering, monitoring, and tests, plus the chance to work on LLM-powered assistants and systems-level Rust work.

I’m a self-taught engineer who builds and ships complete products on my own. I wrote and released Fyt, a fitness app live on the App Store, covering the native iOS and watchOS clients, the TypeScript and PostgreSQL backend, and the CI/deployment behind it.

I’m strongest on backend services and native Apple development—Fastify REST APIs, schema migrations, background jobs, and HealthKit-driven ingestion—so features work reliably in production. I’ve also shipped an in-chat assistant on the Claude Agent SDK, and hardened it with prompt-injection defense using a restricted tool surface, SQL guardrails, and output sanitizing.

Beyond product work, I’ve built production-grade systems in Rust, including a low-latency, fully async market-making/trading system using Tokio, WebSockets, axum, and on-chain settlement on Polygon. I care about engineering process and quality: test suites, CI/CD, monitoring, and documentation so shipping stays fast without sacrificing correctness.

Experience

Work history, roles, and key accomplishments

Current

Software Engineer (Independent)

Current

Independent

Nov 2025 - Present (8 months)

Built and shipped Fyt, a native iOS/watchOS fitness app with a TypeScript/Fastify + PostgreSQL backend and production CI/deployment, including monetization via a live subscription tier. Also built production LLM tooling with the Claude Agent SDK and a Rust trading/market-making system with automated live execution and testing.