The warning “Real-time event processing is currently overloaded and may stop processing your events.” means that the CEP server is at its limit. In this case it might happen that your CEP rules will not work in real-time for a short time or in worst case they can get disabled by the system. This will happen, when the system starts to deactivate the ten most resource consummating CEP rules and if your rule is one of those.
You will see if that happens, when your CEP rule gets undeployed. (it is shown in “Event processing” with a red exclamation mark) If your rule stays online, it is as said. It might not be realtime for the period the overload situation is in place, but all rules are working.
There are simply too many events for the CEP queue to handle, hence the message.
We are working to improve the event processing so the queue does not get overloaded in a future version.