I ran into an interesting problem recently where simple concurrency on the BEAM via Task.async made my application a lot slower and a lot more memory hungry. This blog post illustrates the issue with a short example, where processing 3 non-trivial actions on a list in parallel is slower than doing it sequentially, and then explains why this happens and what can or can’t be done about it.

https://pragtob.wordpress.com/2023/12/18/careful-what-data-you-send-or-how-to-tank-your-performance-with-task-async/