# Cho Yin Yong

> AI Engineering Leader, University Lecturer, and Entrepreneur — building in healthcare AI, developer tools, and enterprise software.

Every page on this site is also available as markdown: send `Accept: text/markdown`,
or append `.md` to any path (for example `/blog/stripe-is-dangerous.md`).

## Pages

- [Home](https://choy.in/) — Cho Yin Yong — AI engineering leader, cofounder, lecturer.
- [Projects](https://choy.in/projects) — Every project and award across healthcare AI, developer tools, and shipped products.
- [Talks](https://choy.in/talks) — Conference sessions and university guest lectures.
- [Teaching](https://choy.in/teaching) — Courses taught at the University of Toronto.
- [Blog](https://choy.in/blog) — Notes on building, shipping, and teaching software.

## Projects

- [lotsotravel](https://choy.in/blog/lotsotravel-case-study) — eSIM convenience store built and shipped in a single season. _(Lovable Shipped S1 · Top 10)_
- [saasmail](https://choy.in/saasmail) — Centralized per-customer inbox for SaaS teams, self-hosted on Cloudflare Workers.
- [opensigma](https://choy.in/opensigma) — Free, open-source Stripe Sigma & Data Pipeline replacement on Cloudflare D1.
- [nitrogen](https://choy.in/nitrogen) — Turn Claude, Codex, and Gemini CLI sessions into shareable images.
- [Youth Mental Health Narratives](https://choy.in/youth-mental-health) — Discovering novel variables for NVDRS data.
- [cite-met](https://choy.in/cite-met) — SEO & AEO visibility tracking for AI-built sites.
- [ziani](https://choy.in/ziani) — Meeting intelligence and workflow automation.

## Talks

- [Converting Free Text to FHIR: Unlocking EMR Data Value with AI and Standards](https://www.youtube.com/watch?v=P1Cdov6CYWU) — FHIR North 2025 · Mohawk College _(October 29, 2025)_
- [Building Applications with Language Models](https://www.youtube.com/watch?v=d0fkbi-hyz8) — Guest Lecture · CSCC01 · University of Toronto Scarborough _(June 4, 2024)_
- [Leveraging Healthcare Virtualization to Compile an International Patient Summary](https://www.youtube.com/watch?v=ngAKtJRIu6U) — FHIR North 2024 · Mohawk College _(October 23, 2024)_
- [FHIR Starter: How AI Can Help Organizations Move from HL7v2 to FHIR](https://www.youtube.com/watch?v=BsAnzg84T2Y) — FHIR North 2023 · Mohawk College _(November 13, 2023)_

## Teaching

- [Engineering Large Software Systems](https://choy.in/teaching) — CSC301 · University of Toronto
- [Programming on the Web](https://choy.in/teaching) — CSCC01 · University of Toronto

## Writing

- [Building Lotsotravel – From a Personal Pain Point to an AI-Powered Global eSIM Store](https://choy.in/blog/lotsotravel-case-study) — How a simple side project evolved into a revenue-generating eSIM platform, the unexpected lessons in global markets, and the hurdles of indie e-commerce. _(2026-03-08)_
- [A game from an Instagram Reel built after 30 minutes](https://choy.in/blog/chess-tic-tac-toe-vibecoded) — I've been on a vibecoding spree recently. It's been a while since I've built something just for the fun of it, and I'm really enjoying the process. _(2026-02-10)_
- [copilot-instructions.md is a great entrypoint for AI coding assistants](https://choy.in/blog/copilot-instructions-game-changer) — Learn how copilot-instructions.md can dramatically improve your AI coding experience and why automating its creation is the future of development workflow. _(2025-11-19)_
- [Stripe is Dangerous: How to Make It Safer for Your Side Hustle](https://choy.in/blog/stripe-is-dangerous) — The day I sold $400 of eSIMs that turned into a fraud wake-up call. Practical Stripe Radar settings, and how to avoid chargeback pain as a side hustler. _(2025-10-18)_
- [Integrating a Custom Backend with Lovable: What Worked and What Didn't](https://choy.in/blog/connect-backend-to-lovable) — Lovable is great for frontends, but what about the backend? Here's how I connected my existing backend service to my Lovable frontend. _(2025-09-25)_
- [5 Game-Changing Steps I used to launch my Lovable Project (And Why Most People Skip Step 3)](https://choy.in/blog/5-crucial-steps-lovable-project) — After 8 years of building everything from appointment booking solutions to AI-powered applications, I find vibecoding to be extremely interesting. Here are the 5 crucial steps I used to launch my latest Lovable project, and why most people skip step 3. _(2025-09-24)_
- [Building a Scalable URL Shortener with Cloudflare Workers and KV](https://choy.in/blog/build-a-url-shortener-with-cloudflare-workers-and-kv) — Learn how to build a cheap, scalable, and serverless URL shortener using Cloudflare Workers and KV, perfect for handling millions of links and users. _(2022-11-23)_

## Optional

- [Sitemap](https://choy.in/sitemap.xml) — every indexable URL
- [robots.txt](https://choy.in/robots.txt) — crawler rules and content signals