We recommend at least two cores and 4GB of RAM. That’s what we mostly use when running interventions on a VM running Ubuntu. MC Designer might get slow when there are too many participants (when it is in the hundreds) but the mobile app should not be affected in a way that disrupts the interventions. If any doubt, go for four cores and 8G of RAM. For disk space, that depends mainly on how big the media files will be, if you use any in your intervention, and if you let your users use media input functionality. For most of our interventions without excessive use of media files, we are using a default 80GB disk for our VMs.