TMS - XDATA - LIMIT ACCESS CLIENT

We have an REST SERVER with XDataServer / XDataConnectionPool / SparkleHttpSysDispatcher / AureliusConnection without any problem and clients with FMX app. But need limit quantity of client user simultaneous access or any specific client user the REST SERVER . Is possible ?

XData is stateless, what do you consider "simultaneous access"? Simultaneous in a single request, or from a client session?

About rejecting a specific client, how do you plan to identify a client?