RStudio Connect has a limit for the number of concurrent users it can serve, which is based on the number of named users for your license type. A concurrent user is defined as a single individual with an active browser connection to one or more customer applications (see 3.2.1 of the End User License Agreement).
Concurrent User Limits
More plainly, a concurrent user can be described as one human on one browser connecting to one instance of RStudio Connect, whether they are an administrator, publisher, viewer, or anonymous visitor, as defined in the RStudio Connect Permissions Document.
The concurrent user limit in your RStudio Connect instance depends on the type of license that you are using. When the number of concurrent users exceeds that limit, additional users will see an error message stating that the license quota has been reached:
Increasing the Number of Concurrent Users
The concurrent user limit in your RStudio Connect instance depends on the type of license that you are using. You can increase the limit for concurrent users in RStudio Connect by purchasing additional user packs.
Refer to the RStudio Pricing page for more information about different license types and purchasing named user packs.
Limits for Named Users and Anonymous Visitors
In RStudio Connect, named users consist of administrators, publishers, and viewers that can log in to the RStudio Connect interface, whereas anonymous visitors are users that are accessing published Shiny apps that are configured to "Anyone - No login required" under the setting for "Who can view this site" in a published Shiny app. For more information about permission levels, refer to the RStudio Connect Permissions Document
Anonymous visitors who are viewing published Shiny apps are counted towards the total number of concurrent users. Anonymous users who are viewing published R Markdown documents or APIs are not counted towards the total number of concurrent users.
In some cases when there are anonymous visitors viewing Shiny apps, you might see that the total number of users (both named users and anonymous visitors) exceeds the upper limit of concurrent users for your license. This functionality is intentional and enables named users to log in to and use RStudio Connect even when anonymous visitors are connected to and viewing published content.
If you are experiencing errors related to license quotas, or are concerned with the standard limit of concurrent users, we recommend purchasing additional user packs to allow for more flexible usage. You can also refer to the Administrator Metrics in RStudio Connect in terms of CPU, RAM, Active Users, and Shiny Connections to understand the impacts of end users concurrently accessing published content.
Examples of Concurrent Users and Connections
A single concurrent user can have multiple connections to RStudio Connect. Every named user that that logs in to the RStudio Connect interface (e.g., administrators, publishers, and viewers) or opens a browser tab to visit a published Shiny app (e.g., named users and anonymous users) establishes a connection to RStudio Connect. When a user runs one or more apps on multiple browser tabs, that user creates multiple connections to RStudio Connect.
Example 1: A user connects to a single Shiny app. Outcome: One concurrent user and one connection.
Example 2: A user connects to the same Shiny app two times by opening two tabs in a browser. Outcome: One concurrent user and two connections.
Example 3: A user connects to two Shiny apps via two tabs in a browser. Outcome: One concurrent user and two connections.
Example 4: A user connects to two Shiny apps using two different browsers. Outcome: Two concurrent users and two connections.
Example 5: A user connects to two Shiny apps on a load balanced cluster and one app is served from one instance and another app is served from another instance. Outcome: One concurrent user and one connection on each instance for a total of two concurrent users and two connections.
For information about how to scale and tune applications in RStudio Connect, refer to this article.