I just had an interview yesterday and took me a long time to solve a problem under pressure (few loops and some dictionaries and list and sorting), later last n

I just had an interview yesterday and took me a long time to solve a problem under pressure (few loops and some dictionaries and list and sorting), later last night at work found some complex issue debugging some packets and code. Is hard to measure what is good. I was thinking that maybe creating a project that is used by hundreds makes you a better one?