Fundamentally, a real time billing system shares many of the same design challenges as an air-traffic control system, a pacemaker, or the space shuttle. Some of the more significant challenges are scalability and performance, reliability, security, and extensibility.

Real time CM&B systems easily scale to handle rapid subscriber growth and large numbers of subscribers while maintaining outstanding performance. Providers can add multiple servers as needed to any or all levels of the system while the system is operational. Automatic load-balancing smoothly handles usage spikes. Indeed, a real time system's object-to-relational model is optimized for high-performance on-line transaction processing (OLTP).

Real time systems provide 24-hours-a-day, 7-days-a-week, telecommunications-grade reliability with features such as automatic reconnection in the event of a lost link and automatic rerouting if reconnection fails. Both features occur without interrupting the client application. In addition, a real time system guarantees transactional integrity through the entire system, maintaining a reliable status on every account. Because they are designed to take advantage of redundancy, adding additional systems to the architecture increases reliability.

Firewalls, proxies, and filters can be installed between every tier of the real time system's architecture to prevent unauthorized access to the database. Providers can determine and audit who has access to the system. Critical business functions run at the secure business process tier, and access lists restrict the use of critical operations. All session monitoring, analysis, and control occur in real time so that problems can be identified and stopped immediately.

Real time systems offer open, documented programming interfaces at every level of the system. These interfaces give providers the ability to integrate a real time system with legacy and external software. Furthermore, real time systems go beyond simply allowing providers to tailor their basic capabilities. Because the system's architecture is extremely extensible, it enables providers to add new, value-added services to their menu of offerings. These can range from capabilities such as cable-modem access and global roaming service to on-line games and entertainment to Web site hosting and Internet telephony.