MISTAKES ENGINEERS MAKE IN LARGE ESTABLISHED CODEBASES

Summary from the TLDR Web Dev newsletter

Working in large, established codebases is challenging, requiring skills not learned in smaller projects or open source contributions. The most important skill is maintaining consistency by following existing code patterns and avoiding isolated, "clean" implementations. Understanding the codebase's production usage, particularly high-traffic areas, is also really important, as is careful testing and monitoring due to the impossibility of exhaustive testing.