Awesome! I'll investigate how easily we can stream our JSON out.

Its probably not worth changing it if it is eg in a file already, but if the process to generate it is a slow one it might be.

I agree. If you're doing something slow/asynchronous like aggregating several http resources it is worth it to write out as early as you can but keep server-side the same if you can generate the whole JSON quickly.

One issue I found with writing early is handling error condition(s).

On the server side, you may run into an error after you started writing out your reply. That may cause an incomplete reply. It may require more involved error handling between the server and client. 'Gather first write later' approach gives you a simpler error propagation between server and client.

Nope, just parsing some results back from MySQL.

here's a streams2 library for streaming to the client as an array: https://github.com/stream-utils/streaming-json-stringify