Architecture patterns in legacy systems

Understanding and successfully modernizing established structures

In every large company, operational information systems map business-critical processes. Large sums are invested in their creation and further development every year and many systems are developed and maintained over decades. Over time, however, ideas about good software architecture change and, of course, the developers responsible also change. New colleagues often find it difficult to recognize, understand and use the existing programs and the originally designed structure. Software that has been successfully operated for years is then quickly labeled as “unmaintainable” or “legacy”.
However, our experience shows that many old systems do have well thought-out structures. The developers of the time sometimes achieved amazing things with primitive means. Those who understand historical architectural patterns – even if they were not described as such at the time – have a key to successful maintenance and efficient modernization.