My understanding from reading this is the complete opposite. This library is explicitly not supporting the features that web servers need to be performant and handle production traffic, like streaming.

A web server using this could only start parsing when it receives the last byte, and could only start responding when it’s done serializing, all while holding non-lazy trees of JsonValue objects in memory.

I suspect the vast majority of services are not dealing with such massive JSON documents that doing serde on them becomes a material part of their latency breakdown.