asynchronous - Mule 4 Async vs VM Scope, which is more preferred to use for processing flow asynchronously?

Question

from what I can comprehend briefly, both of them processing flow asynchronously with VM scope using more resource as it create new context, separate properties and variables. Any particular reason other than that if the use is just to process the flow asynchronously?

Answer 1

Async is a scope that is executed immediately in parallel with respect to the flow, if there are resources available (ie threads). VM is a connector that implements an in-memory queue. I usually recommend to prefer to use the VM connector because with Async if there are no threads available it can fail to execute. With the VM connector the messages will be queued until the flow that reads from the VM queue is able to read the next message. Note that if the number of messages queued is greater than the number of messages processed it will run out of memory or exceed the queue allocation, causing another error.

Always remember that threads are a limited resource. In Mule it is not possible to control the number of threads used, only the concurrency. Also keep in mind that threads are not free, they consume memory and CPU.