Just like the title. I would of tried wrapping a more performant one (Jackson, Jsoniter, etc.) but then I noticed that the json library is used inside the jServer library for websocket communication therefore this wish ...
There wasn't ever any report of a performance problem with the existing library.
It takes an average of 3ms to parse a 173KB (5700 lines) json file generated with: https://www.json-generator.com/
It takes 0.2ms to parse a small json file, similar to the json strings sent during WebSocket communication.
I don't think that it will ever be a bottleneck in a server solution.