Matryoshka Code
Probably the funniest meetup I ever gave, its topic still pops up in conversations, even six years later in 2025.
Slides: 
https://matryoshka-code.now.sh
pitch
I’m gonna rant about matryoshka code, DRY as dunes of Arrakis, and utmost unpleasant to work with. Have you heard about it? Are you guilty of writing it? I’m going to describe the problem and propose a few ideas of how to deal with it.
tldr
instead of making chains, grow trees
—yours truly, Wrocław, 2019
duplication is far cheaper than the wrong abstraction