Performant: I do not think it means what you think it means.
Around Microsoft, people talk about making things performant. They mean "fast" or "performs well".
It is a real word, but according to OED, it means a person who performs something.
In any case, I think it really isn't all that important (that is a "real word"). I know what they mean, they know what I mean, and isn't that the point?