I was going to post this, but then I realize Jeff Boulter already posted about this.  I come to a different conclusion, though.

Every time I hear 'performant', I cringe... it's like fingernails on the chalkboard, or like when I hear (occasionally) people say 'authentification.' 

Look it up, 'performant' is not a word.  Can we put this long, lexical nightmare behind us, please?

Before:

I want the system to be as performant as possible.

After:

I want the system to perform very well.