The Danger of Architectural Technical Debt: Contagious Debt and Vicious Circles

A known problem in large software companies is to balance the prioritization of short-term with long-term viability. Specifically, architecture violations (Architecture Technical Debt) taken to deliver fast might hinder future feature development. However, some technical debt requires more interest to be paid than other. We have investigated which Technical Debt items generate more effort and how this effort is manifested during software development. We conducted a multiple-case embedded case study comprehending 7 sites at 5 large international software companies. We found that some Technical Debt items are contagious, causing other parts of the system to be contaminated with the same problem, which may lead to non-linear growth of interest. We also identify another socio-technical phenomenon, for which a combination of weak awareness of debt, time pressure and refactoring creates Vicious Circles of events during the development. Such phenomena need to be identified and stopped before the development is led to a crisis point. Finally, this paper presents a taxonomy of the most dangerous items identified during the qualitative investigation and a model of their effects that can be used for prioritization, for further investigation and as a quality model for extracting more precise and context-specific metrics.