Well, her github profile pic is "I ️ 35000 lines in gc.cpp". She's been working on it successfully for 15 years so I guess she's untouchable even within the org (I can't imagine the amount of stress she went through over the years). Aside from issues with a 35K source file, being a deep domain expert with a singular focus seems awesome.
https://github.com/Maoni0
https://www.youtube.com/watch?v=ujkSnko0JNQ