It was not a complaint, it was a question, just like my top-level comment.

Was that interpreted as a complaint as well? Is that the problem?

It sounded like complaining but either way, take a look at these.

https://news.ycombinator.com/newsguidelines.html

"Please don't comment about the voting on comments. It never does any good, and it makes boring reading."

A concurrent map in my understanding, is a map that can be accessed concurrently without explicit synchronization, not each coroutine has a piece of it. Check java ConcurrentHashMap.