Abstract: A computer telephony integration (CTI) client computing device isolates call processing devices from each of a set of back-end business applications of call-center clients for which call-center services are provided. A registered call event is received from a CTI middleware server during active call processing of an incoming telephone call responsive to an interactive voice response (IVR) system storing real-time call data to an independent stand-alone database in association with a unique call-specific database key. The unique call-specific database key is retrieved from the CTI middleware server. A call database record, including the real-time call data, is retrieved from the independent stand-alone database using the unique call-specific database key retrieved from the CTI middleware server. The real-time call data is provided as output to a trusted call center agent that has separate authorization to access a back-end business application appropriate to continue the active call processing.