We detached this subthread from https://news.ycombinator.com/item?id=14860331 and marked it off-topic.

"performing at the highest level"

http://www.urbandictionary.com/define.php?term=Killing+It

Doing extra-ordinary well, or even just "doing great" or "doing very well".

Usually, "it" in "killing it" refers to some kind of game, so they're "killing the game", or doing a really good job beating the game.

Definitions for "killing it":

1. Performing a task exceptionally well.

2. Facebook

Slang for "doing very well".

Ex: "You got an A on that midterm? Dang Carl, you're Killing it!"

"Doing really well".

Heard in the context of many competitive activities.

E.g. at a jazz club, someone might say "He's killing it, man!" if they were really connecting to what the trombonist was doing.

doing really really well :)