recently I stumbled upon one of the most frequent integration scenario namely message queueing. An external application calls scpi which saves data in SAP. SCPI performs a duplicate check before sending data to SAP. This works fine if the external application calls SCPI in two different times. But the duplicate check prooves ineffective if the external application calls SCPI twice at the same time: there's no room for SAP to persits data from the first call and letting SCPI check wheteher those data have been persisted before sending those of the second call.
It's quite a common issue but since I moved from SAP PI/PO to SCPI I never found a suitable alternative.