An Active Hour is an hour that an instance of an application is up and serving requests. Whether you have one or one hundred people using one instance of your Shiny app for an hour, you are still only using one active hour. However, if you have only one person actively using two different Shiny apps for one hour at the same time, you are consuming two active hours in that time. If you have configured your application for multiple instances to enhance performance as more people use it (available in Basic plans and above only), each instance of the application uses active hours as if it were a separate app.
When an application hasn’t received any traffic for some time (the idle period) it will put itself to sleep. This stops active hours from accruing. When a user requests an application, shinyapps.io will “wake up” your application so that it is running and capable of servicing the request.
TIP: While we believe the number of Active Hours included in each plan is generous, to reduce the rate of Active Hour consumption you can shorten the time an application remains ready to respond if users are idle. By default it is set to 15 minutes.