I bought a book a couple of years ago: iOS and macOS Performance Tuning. I took note that the author had not used the word "performant" even once in the book's 400 pages. Maybe I'm a snob, but it made the author seem the more credible to me.
In my native Romance language it is written the same and it's an usual word. I never thought that it's a neologism in English and perceived as pretentious.