Agentic Engineering at Scale

Chapter 1. Inside-Out Reverse Engineering

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Real companies have existing codebases. These codebases are often large, running from hundreds of thousands of lines of code to tens of millions. There are usually many interrelated applications, known collectively as legacy estates. In typical companies, most revenue runs through these decades-old legacy estates. In my twenty years as a software consultant, the majority of my clients have been in this position. The others were companies under ten years old.

Due to their age, these systems are hard to safely change. In order to move forward, companies must preserve what is useful about them while migrating to a new implementation. To do that, they must reconstruct the processes that are managed by the legacy systems. Modern software is so complicated that for old systems, no one can say exactly what it does or what it’s supposed to do. This is where reverse engineering comes in.

Reverse engineering is the production of a validated model of an existing system that is fit to guide deliberate change. That model must ...