I won't argue about complexity since i don't know the code base. I just saw statement about performance improvement which sounds like it motivates the changes. Its a common way to sell shiny approach by telling it will work faster. So i couldnt resist to throw some shit on it. You seems to be trigered by "waste of time". I probably could write in a more friendly manner but have a little english communication expirence so i just wrote what i have in my mind. In development it happens all the time u do something what is not worth speending time on it. I dont really know was it worth or was not. I didnt give any advice, it was an argument.

I think u can try better. I dont mind if you will be rude(actually your last post is toxic so whats the difference) There should be a reason for switch to non blocking approach so just write it. Maybe u can share perfomance numbers. How many memory blocking code was consuming per call?

Sounds like you higly increased code complexity in return for nothing. JVM allocates 1mb per thread. How many parallel blocking request client does? I assume that number is not big. You can even reduce memory per thread using jvm option. 512kb most likely is enough.