The principle of Chesterton's Fence advises understanding why something exists before removing it, which is crucial for navigating the hidden complexities of legacy code.
The oldest unfixed bugs in a system act as a form of memory, revealing areas that are too complex, risky, or culturally contentious for the team to address.
Analyzing commit history with tools like CodeScene reveals hidden couplings between modules that architectural diagrams miss, preventing catastrophic failures like the Knight Capital incident.
Technical analysis tools are insufficient without a team culture of psychological safety where engineers feel empowered to halt a release when something seems wrong.
Intermittently failing or flaky tests often act as canaries, probing unintended system behaviors that are not captured by their explicit assertions.
The core discipline is not about preserving old code, but about asking "why" to understand the context and constraints that led to its creation before making changes.
Jobs that call for the skills explored in this talk.