Are you asking how much traffic can your store handle, checkouts per minute, something else?
Traffic wise that's not something you need to handle. It will handle it.
What kind of numbers are we talking about?
Just curious how many people you give access to. It seems a lot of people serve to a large number of people. I think two people access my stuff so I am not too concerned about server power. At what point did you tell yourself you need a beefier setup?