Ask HN: What's your favorite Node.js interview question?

I've been a full time PHP developer for years, but node is my goto language for side projects. My new year resolution is to find a node job. I am putting together a cheatsheet of Node.js interview questions at https://www.cheaki.com/nodejs/nodejs-interview-questions and wanna get some inputs from the HN and wanna get more questions. What's your favorite Node.js interview question (ask or being asked)? Thx!