I can envision a weak prediction mode which is what (certain abilities? All abilities?) fall back to when there is no fresh prediction key that can accurately correlate side effects. When in weak prediction mode, perhaps only certain actions can be predicted - for example GameplayCue execute events, but not OnAdded/OnRemove events. FPredictionKey is a generic way of supporting Clientside Prediction in the GameplayAbility system. A FPredictionKey is essentially an ID for identifying predictive actions and side effects that are done on a client. UAbilitySystemComponent supports synchronization of the prediction key and its side effects between client and server.