Guanzhong Chen
Software Engineer at DMOJ: Modern Online Judge
Old Toronto, Ontario, Canada
Summary
🤩
Rockstar🎓
Top SchoolGuanzhong Chen is a software engineer with 15 years of experience, currently building payment infrastructure at Stripe and co-running DMOJ, a widely used open-source online judge he helped scale to 20,000 users and support 60+ languages. A University of Waterloo software engineering graduate, he has deep systems and back-end expertise demonstrated by contributions to WebAssembly toolchains (Binaryen, Emscripten) and Clang—work that improved sanitizer support, stack-safety checks, and Wasm-specific codegen. He combines production-grade engineering with platform-level security and reliability work, from defending DMOJ against large DDoS attacks to shipping two-factor and biometric auth features at Stripe. Guanzhong’s open-source footprint includes creating scalable sandboxed execution environments and enhancing sanitizers for WebAssembly—an uncommon niche that bridges compilers, runtime safety, and distributed execution. He prefers solving low-level, correctness-critical problems that make higher-level services safer and more scalable. Based in Old Toronto, he balances long-term platform stewardship with day-to-day feature delivery.
15 years of coding experience
2 years of employment as a software developer
High School, High School at Don Mills Collegiate InstituteSoftware Engineering, 95.22%, Software Engineering, 95.22% at University of Waterloo
Chinese, English
Stackoverflow
3,802reputation
989kreached
65answers
3questions
console
top-5%
python
top-5%
Github Skills (35)
debugging10
debug10
c-language10
python10
back-end-development10
django10
llvm10
memory-management10
c1110
c1710
compiler-compiler10
fifo10
compiler10
emscripten10
webassembly10
Programming languages (23)
Github contributions (5)
DMOJ/online-judge
Mar 2014 - Jan 2023
A modern open-source online judge and contest platform system.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:343 reviews, 5478 commits, 688 PRs in 8 years 11 months
Contributions summary:Guanzhong primarily focused on back-end development within the open-source online judge system. Their contributions involved implementing new features such as adding views for kicking users and modifying existing views, particularly within the organization management system. They also made significant updates to the database schema and related files, adding support for a more advanced feature set. The user's work encompassed modifications to both application logic and database structure to improve system functionality.
dmojpythoncontest-platformdmoj-judgeonline-judge
emscripten-core/emscripten
May 2019 - Sep 2020
Emscripten: An LLVM-to-WebAssembly Compiler
Role in this project:Back-end Developer
Back-end DeveloperContributions:1 review, 79 commits, 166 PRs in 1 year 4 months
Contributions summary:Guanzhong primarily focused on enhancing Emscripten's support for the Undefined Behavior Sanitizer (UBSan) and LeakSanitizer (LSan) runtimes, which involved integrating these sanitizers for Emscripten's LLVM-to-WebAssembly compiler. Their contributions included adding necessary code, making the runtimes functional within the Emscripten environment, and improving stack trace support for debugging. These efforts improved the ability to detect memory errors and vulnerabilities. The user also fixed various bugs within the test suite that were uncovered through the usage of AddressSanitizer.
emscriptenwebassemblycompilerwasmllvm
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