[dep_b]

JSON performance is super important for a server, far more than for the usual macOS or iOS clients. JSON parsing might be based on the basic JSON parser found in Swift, which isn't fast at all, rather easy to use and secure instead.

It's not super up-to-date but you can see there's definitely some competition even on Swift level in terms of JSON performance. https://github.com/bwhiteley/JSONShootout

Swift JSON encoding/decoding should approach C/C++ levels of performance when optimized for speed.

[abalone]

The plaintext benchmark was also slow, so the JSON implementation may not be the main cause here.