I'd argue the message queue is, itself, likely not needed. Not directly.

I think, ideally, for a system to be successful, you need to understand all places that you either build up messages, threads, buffers, whatever. It ultimately doesn't matter which you do. Just don't do too many. And don't make migrating a solution from one type to another part of your critical path to launch. Logging, in particular, is something I've grown tired of people reinventing before they have even launched.

Obviously, you don't need an external message queue to have a functioning system, only to have one that meets the article's definition of a “well-architected monolith”.

Play framework has support for this via akka and it works quite well from my experience ^^