Decoding JSON is surprisingly intensive. Check out this to see what's going on with it in Dotnet: https://michaelscodingspot.com/the-battle-of-c-to-json-seria... .

Node.js will have that issue and in fact the stdlib JSON encoding/decoding can't even be paused so once you start a processing something you're stuck until it's done. You could, however, write an incremental serializer/deserializer that could spread processing out across many event loop cycles to mitigate.

Go, ASP.NET, and others not so much, depending, because the schedulers can pause and resume the tasks(on top of being threaded).