Reloading shiny app partially


I am just getting started with shiny, so this may be a very basic question. My app imports a large dataset, so it takes a while to initially load. If I make even tiny modifications to the code (like changing the plot color scheme), I have to reload the app to see them and that takes a long time. Is there a way to somehow cache certain parts? For example, if none of the objects are getting modified, can they be reused?