A longitudinal study of identifying and paying down architecture debt

Architecture debt is a form of technical debt that derives from the gap between the intended and the actual architecture design. In this study we measured architecture debt in two ways: 1) in terms of system-wide coupling measures, and 2) in terms of the number and severity of architecture flaws. In recent research it was shown that the amount of architecture debt has a huge impact on software maintainability and evolution. Consequently, reducing debt is expected to make software less costly and more amenable to change. This paper reports on a longitudinal study of a healthcare communications product created by BrightSquid Secure Communications Corp. This young company is facing the typical trade-off problem of desiring responsiveness to change requests, but wanting to avoid the ever-increasing effort that the accumulation of quick-and-dirty changes eventually incurs. In the first stage of the study, we analyzed the status of the "before" system, which showed the impacts of change requests. This initial study motivated a more in-depth analysis of architecture debt. The results of this debt analysis were used in the second stage of the work to motivate a comprehensive refactoring of the software system. The third stage was a follow-on architecture debt analysis which quantified the improvements realized. Using this quantitative evidence, augmented by qualitative evidence gathered from in-depth interviews with BrightSquid's architects, we present lessons learned about the costs and benefits of paying down architecture debt in practice.