I worked at a startup that indulged in pair programming thing. Where as a junior, you'd be partnered with a senior developer.

My mentor, always insisted on having shortest variable names possible, so that the "size of codebase" will be very small.

It was a nightmare going through his code and understanding what's he's done. Best part, no comments as well.

In a way it has primed me to go through any codebase possible.