MarkUs: Index
| From Open Source Contributions | |
| MarkUs | |
|---|---|
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| First created | Mar 22, 2026 |
| Last edited | May 26, 2026 |
MarkUs is a Ruby on Rails application used by every Computer Science course at the University of Toronto for assignment submission, automated grading, and TA-driven manual grading. Thousands of students submit through it every term; hundreds of TAs grade through it. The codebase is over a decade old, ~150K lines of Ruby + JavaScript, deployed at multiple Canadian universities.
Working in MarkUs is a different problem from greenfield engineering. The hard part isn’t usually the change — it’s loading enough of the surrounding code into your head to be sure the change doesn’t break some assumption three modules over. Most of what I learned that summer was about how to read large Rails codebases, how to trust the framework where it knows better than you, and where the framework’s defaults stop being safe at scale.
The three articles below are the patches I’d actually defend in an interview.
