Have you moved into a public cloud lately? The first step is to choose the size of the machine instance from a standard machine configuration that has enough vCPUs and enough memory. Of course, cloud providers offer custom machine instances, so you can pick the exact right amount of vCPUs and memory.
But whether it’s a standard or a custom machine instance, enterprises simply guess at the correct size, using on-premises systems as a guide. It’s a logical approach, but it’s not realistic. You rarely run the same workloads on the same server types in the clouds. Moreover, most applications will undergo some refactoring before they end up in the cloud. It’s apples and oranges.