Hi! I’m Joseph Liu, a third-year undergraduate student at the University of Waterloo double majoring in computer science and pure mathematics.

I love to program in my free time, and have built and contributed to various projects over the years—more on those below. Aside from programming, I also enjoy reading, writing, math puzzles, and the occasional anime.

Programming experience and projects

Nowadays, I primarily work with Rust and Go on backend projects; however, I am comfortable working across the entire stack and have experience in Python, TypeScript, Swift, Java, and C++ among other technologies.

Contributions to YAGPDB

Most of my open-source work centers around the YAGPDB project, a large-scale distributed Discord bot for which I am an administrator and code contributor. I have written 130+ patches for YAGPDB over the years. Besides addressing a whole bunch of user suggestions and reported bugs, some of my personal highlights include

  • building core language features and security hardening for YAGPDB’s custom scripting engine;
  • collaborating with a small team of contributors to move the documentation off GitBook to Hugo, cutting load time for tens of thousands of viewers;
  • and migrating multiple legacy plugins away from GORM to SQLBoiler, impacting several hundred million database rows.

Other than the main YAGPDB project, I have also worked on a language server and VS Code extension for YAGPDB’s custom scripting language. As part of this project, I implemented an error-tolerant and lossless parser generating a CST with rowan, a symbol resolution algorithm, and a Wadler-style pretty printer. The last subsystem was developed in collaboration with GPT-5.6 Sol as an experiment with agentic development.

Other open-source projects

  • obscenity: A popular profanity detection library for Node.js written in TypeScript. I designed and implemented its extensible transformer-based architecture, and wrote extensive tests with Vitest and fast-check.

    Obscenity is used by hundreds of open-source projects and in various corporate applications, and is downloaded 250k+ times weekly on npm.

  • markpdf: A command-line utility to edit PDF bookmarks using a convenient indentation-based format, built in Go.

  • liftoff: An interpreter for a toy programming language, built with Python. Though basic, the language is sufficiently complete to build some interesting programs.

  • yagpdb-cc: A community collection of custom commands for YAGPDB. I created and continue to maintain this project, having reviewed submissions from 30+ contributors over the years. I’ve also built some supporting automation which has seen use in other YAGPDB-related projects.

  • vsHacks: A now-annual hackathon I founded in high school, organized by my programming club in collaboration with other high schools across Greater Vancouver. I led work on the hackathon website and helped run workshops during the event, which saw 50+ participants from the district and beyond.

Professional experience

  • In Summer 2025, I interned at TD Bank as a software developer on the Enterprise Innovation team, where I prototyped an open banking integration using Plaid.
  • In Summer 2026, I interned at Bloomberg L.P. as a software engineer on Bloomberg Vault, where I designed and shipped a distributed concurrency limiter for a high-volume Airflow pipeline.

Contact

I’m happy to chat! You can reach me through jliu1602 [at] gmail.com or via Discord (username jo3_l.)