Only 3% Got It Right: 5 Dangerous Ruby on Rails Code Patterns from RubyKaigi
February 9, 2026
At RubyKaigi 2025, a deceptively simple Rails code quiz was presented at a booth. It looked like everyday production code — nothing exotic, no trick questions.
About 100 developers attempted it.
Only 3 answered everything correctly.
This article is based on the talk “Only ~3% got everything right: 5 common but dangerous Ruby on Rails code patterns” , presented by Yuta Nakashima (Backend Tech Lead at Hubble, Inc.) at Kaigi on Rails 2025. The original material was derived from real production issues and later expanded into a full conference session 全問正解率3____RubyKaigiで出題したやりがちな….
What makes this talk especially valuable is that it doesn’t focus on new features or trends. Instead, it exposes mistakes that experienced Rails developers still make — not because they don’t know better, but because these pitfalls hide inside “normal-looking” code.
Let’s walk through the key lessons.
👉 Read the full article.
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