Extensibility and Refactoring Questions

Approaches for extending existing systems with new functionality and safely refactoring to improve maintainability. Candidates should discuss identifying extension points, designing stable interfaces, minimizing breaking changes, writing and updating tests, applying appropriate abstractions and design patterns, and performing incremental refactors to reduce risk. Evaluate trade offs between short term fixes and long term architectural work, as well as communication strategies to align the team during refactors.