KB246, I have a very similar question Minimize delay in starting Shiny app
I found this on SO: https://stackoverflow.com/questions/39044169/can-you-put-a-shiny-progress-bar-in-global-r
Carl writes:
Each time someone goes to your URL it initiates a new instance of R, which will have to reload the CSV, so yes the CSV will be reloaded. – Carl Aug 19 '16 at 18:21
Based on Carl's response having the data preloaded in memory and ready to go for everyone who comes along sounds unlikely.
I hope I am proven wrong.