I can't think of a scenario where JSON handling is our bottleneck; almost all of the massive-data-handling tasks in my entire career have usually been handled by our database of choice.
Largest individual JSONs we've had to handle like on import tasks and such were about 300mb, which proved extremely easy to manage with stuff like JSONStream -I think we used a hand-rolled analogue back then but JSONStream is actually pretty cool, check it out-
What is the use case here? data lakes?