The missing thing last time I looked was a fast python json library that's byte-compatible with stdlib -- same inputs, same outputs. There are good fast options

The missing thing last time I looked was a fast python json library that's byte-compatible with stdlib -- same inputs, same outputs. There are good fast options but they tend to add some (perfectly reasonable) limitation like fixed indentation size, for the sake of speed, that blocks them from being dropped into an existing public API.