Yeah but AWS doesn't guarantee that "2x m5.xlarge" will meet any kind of performance requirements, particularly your own application's, do they? So you may sud

Yeah but AWS doesn't guarantee that "2x m5.xlarge" will meet any kind of performance requirements, particularly your own application's, do they? So you may suddenly find that your own performance requirements, that were previously satisfied by "2x m5.xlarge" are no longer being met by that configuration, and I doubt AWS will just provide you with more resources at no additional charge.