A large number of Ruby applications run in the cloud today. There are many providers of deployment infrastructure, but the better ones tend to be expensive. So you often have to find the optimal compromise between the price you pay and the resource limits you get for that price.
Hosting providers usually emphasize the number of CPU cores and the size of the storage in their pricing plans. Both these numbers are irrelevant. CPU performance is usually not a problem, and storage can be easily added. Here are what I believe are the most important criteria when evaluating the potential deployment stack:
Total RAM available.
After reading this book, it should be no surprise that memory comes first in my list. ...