The phrase "young librarian" refers to a person who is relatively new to the profession of being a librarian and is in the early stages of their career. Full definition
When I was younger librarians managed knowledge with the books in their collection. (goodereader.com)
It is easy for younger librarians to get carried away with wanting to offer ebooks, audio books, and video content to their patrons. (goodereader.com)
Who, you might wonder, is this man who gladdens the hearts of young librarians, middle - aged professors, and, I am told, droves of retirees? (firstthings.com)