Performant: I do not think it means what you think it means.

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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?