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Charles Tsoi

Selected work

Problem → what was built → outcome

Career and product work across AI, mobile, and enterprise systems. Each card is grounded in a real role, stack, and result — not self-rated scores.

Where I usually contribute.

AI & ML

In production

Built LungLens — a full-stack AI health literacy tool using Hugging Face inference API (live at lunglenshk.vercel.app). Helped design an LLM-based monitoring agent at AAHK using Power Automate + Dynatrace API + ServiceNow.

Product Management

14 years delivering

Fourteen years across Apple, HKJC, Cathay Pacific, and AAHK. At Cathay Pacific, the mobile app grew from ~10,000 to ~120,000 monthly active users (12x) during my ownership.

Event-Driven Architecture

Deployed at HKJC

At HKJC, worked on a Solace migration — moving infrastructure from traditional REST APIs toward event-based messaging.

Edge Computing

Shipped at Apple

At Apple, contributed to docserverless — moving numerical computation from server-side to edge user devices.

Here’s a selection of work I’ve been part of — some enterprise delivery, some products I’ve built myself.

Production agents and full-stack ML products

LungLens

In production

Full-stack AI health literacy tool — live in production

Role
Solo — design, frontend, backend, deployment
Stack
React + Python + Hugging Face Inference API, deployed on Vercel
Problem
Patients struggle to understand chest X-ray results in plain language.
What I built
Bilingual (EN/繁中/簡中) educational tool that helps patients understand their chest X-ray results. Users upload X-ray images for anatomy-focused, plain-language educational analysis — explicitly not a diagnostic tool.
Outcome
Live at lunglenshk.vercel.app
MLLLMProductionReact + Python

End-to-end AI/ML app I designed and shipped alone — Hugging Face inference, Vercel frontend, bilingual UX.

AAHK LLM Monitoring Agent

In production

Automated infrastructure health reporting for senior management

Role
Product lead — gathered requirements, designed approach, managed vendor delivery
Stack
Power Automate + Dynatrace API + ServiceNow integration
Problem
Senior management relied on manual infrastructure health reports (CPU, RAM, downtime).
What I built
LLM-based monitoring agent that automates infrastructure health reporting via Power Automate, Dynatrace API, and ServiceNow. Led product design and vendor delivery — not coded solo.
Outcome
Estimated 80% reduction in manual reporting time
LLM AgentsEnterpriseAAHK

Enterprise AI delivery at AAHK — requirements, design, and vendor management, not a solo coding story.

Mobile and consumer products — PoC to live

Cathay Pacific Mobile App

In production

Airline mobile app — lifecycle ownership over six years

Role
Product Manager / Product Owner
Stack
Mobile app integrated with legacy Passenger Service Systems (PSS)
Problem
Cathay needed a modern mobile experience wired into legacy PSS backends.
What I built
Led product ownership for the Cathay Pacific mobile app — backlog, stakeholder negotiation, and XML/JSON integration with legacy PSS.
Outcome
Grew monthly active users from ~10,000 to ~120,000 (12x growth)
ProductMobileCathay

Six years of lifecycle ownership — not a launch-and-leave story. MAU grew roughly 12x.

北辰 (North Star)

In Progress

Bazi/ZiWei astrology app inspired by Co-Star — targeting iOS

Role
Solo founder — design, architecture, development
Stack
React Native (planned)
Problem
Chinese astrology (Bazi/ZiWei) lacks a modern, Co-Star-quality mobile experience.
What I built
Designing North Star — user stories mapped in Notion, preparing the React Native codebase for iOS.
Outcome
Design phase — in progress
In ProgressMobileiOS

Current build focus — astrology product design for iOS, not vaporware: stories mapped, codebase next.

Event-driven, edge, and enterprise delivery

HKJC Solace Migration

In production

Event-driven messaging for regulated real-time systems

Role
Product Manager / IT Solutions Analyst
Stack
Solace Event Mesh (Pub/Sub)
Problem
Core infrastructure depended on traditional REST API patterns under high concurrency.
What I built
Led Solace migration — moved core infrastructure from traditional API architecture to Solace event-based messaging for real-time odds and betting flows.
Outcome
Event-based messaging in a regulated, high-concurrency environment
Event-DrivenSolaceHKJC

HKJC Solace work — REST to event mesh in a compliance-heavy setting.

Apple docserverless

In production

Edge computing for numerical workloads

Role
Product Manager (Engineering Project Manager)
Stack
Edge / serverless — computation on user devices
Problem
Numerical computation ran server-side, adding latency and infrastructure cost.
What I built
Led the docserverless project — moved numerical computation from server-side to edge user devices.
Outcome
Computation shifted to the edge on user devices
Edge ComputingAppleServerless

Apple edge project — architectural review discipline applied to moving compute off the server.

Side projects and experiments

Hermes

Side Project3

ExpiryScanner — barcode + AI mobile app

Role
Solo builder
Stack
React Native + Expo + GPT-4o-mini + Supabase
What I built
Barcode scanning, AI product ID, Supabase backend, and push notifications — full product loop.
App DevGenAIMobileReact Native + Expo

AI Agent X-Ray

Side Project

Interactive agent tool-calling visualizer

Role
Solo builder
What I built
Side-by-side chat and x-ray view of LLM tool calling — how I explain agent architecture to stakeholders.
LLM AgentsAIArchitectureHTML + JS

Product Tax Deduction Log

In Progress

Mobile app for product purchases and tax deductions

Role
Solo builder
Stack
React Native + Expo
What I built
Personal finance utility for tracking product purchases and tax-deductible expenses. App Store submission in progress.
In ProgressMobileFinanceReact Native + Expo

localLLM

Side Project2

Local LLM experimentation

Role
Solo builder
What I built
Hands-on local LLM evaluation — latency, cost, and fit before vendor recommendations.
MLLLMEvaluationPython

Happy to go deeper on any of these — architecture decisions, stakeholder trade-offs, or how I’d approach your problem.

Short on time? Show LungLens and the AAHK LLM agent, then link to full experience.