What would a company like Thoughtbot look for in a senior engineer?

Hey guys,

It’s not about trying to apply to Thoughtbot. I am asking the question so that I can set some goals to reach as a mid-level engineer. I know that I would never stop learning, but I want to see what are some “must-have” knowledge or experience top-notch companies like Thoughtbot would look for in a senior engineer (such as must have contributed to open source, must know differences between Proc and lambda, etc.). Shall I go for depth or breadth? I get jobs done at work, but without seeking out ways to improve myself, I feel my skills will be stagnant.

Thank you so much in advance!

This is from: Jobs - thoughtbot

thoughtbot web developers are able to rapidly build high-quality Ruby on Rails applications, fully test-driven. Well-qualified candidates have an excellent knowledge of HTML, CSS, JavaScript, SQL, Unix, deployment, performance, debugging, refactoring, design patterns, and other programming practices.