IBM Watson was using Prolog when it won in a Jeopardy! game: "We required a language in which we could conveniently express pattern matching rules over the parse trees and other annotations (such as named entity recognition results), and a technology that could execute these rules very efficiently. We found that Prolog was the ideal choice for the language due to its simplicity and expressiveness."[0]

[0] https://www.cs.nmsu.edu/ALP/2011/03/natural-language-process...