Production Quality Code Organization Questions

Practices for organizing code so it is maintainable, observable, and testable in production. Topics include module and package layout, separation of concerns, defensive error handling, structured logging, metrics instrumentation, abstractions for infrastructure dependencies, ensuring testability with dependency injection or inversion of control, and strategies for incremental rollout and safe releases. Candidates should be able to articulate patterns that make code easy to operate and troubleshoot in live environments.