Quality attribute conflicts - experiences from a large telecommunication application

Modern telecommunication applications must provide high availability and performance. They must also be maintainable in order to reduce the maintenance cost and time-to-market for new versions. Previous studies have shown that the ambition to build maintainable systems may result in very poor performance. The authors evaluate an application called SDP pre-paid and show that the ambition to build systems with high performance and availability can lead to a complex software design with poor maintainability. We show that more than 85% of the SDP code is due to performance and availability optimizations. By implementing a SDP prototype with an alternative architecture, we show that the code size can be reduced with an order of magnitude by removing the performance and availability optimizations from the source code and instead using modern fault tolerant hardware and third party software. The performance and availability of the prototype is at least as good as the old SDP. The hardware and third party software cost is only 20-30% higher for the prototype. We also define three guidelines that help us to focus the additional hardware investments to the parts where it is really needed