Baristas normally aim to grind coffee finely to maximise surface area and extract the most coffee compounds, but a mathematical analysis has found that coarse grounds are better as they reduce clogging
Source:
https://www.newscientist.com/article/2231003-maths-says-you-need-coarser-coffee-grounds-to-make-a-perfect-espresso/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home