The external activate workstep/complete workstep events are parked in the persistent store till the target workstep is reached in the process flow. The scheduler periodically checks for the eligible external event, performs the operation specified in the event and then marks the event as processed. Another scheduler job moves these marked events to the history table. While processing the events, the scheduler moves events with incorrect data to invalid events' table.

BP Server can handle the out-of-sequence events if its process instance is not yet created, completed, or removed. Events for completed and removed process instance are moved to invalid events' table. Events received for a process instance before it is created are moved to invalid events' table after making a fixed number of retries.

BP Server can handle following cases of out-of-sequence events.