I stumbled across this C++ library: simdjson
It's tag line:
JSON is everywhere on the Internet. Servers spend a lot of time parsing it. We need a fresh approach. The simdjson library uses commonly available SIMD instructions and microparallel algorithms to parse JSON 2.5x faster than anything else out there.
My first thought was "Is there no comparably fast library written in Rust?" And if there is, is it really that much slower than this C++ implementation?