How many apps can we host on Shiny Server Pro simultaneously?

There is no limit to the number of apps you can host simultaneously. However, there is a limit to the number of concurrent connections that can be made to your server. A concurrent connection is equivalent to a tab on a browser and it is common for one person to have more than one tab open and connected to Shiny Server Pro at a time in our experience. The concurrent connection limit is per server. If you are going to have more than a handful of users at the same time we generally suggest you consider the bigger server, which offers a significantly lower cost per concurrent connection.