Maintainability and Legacy Code Questions

Covers strategies and principles for evolving codebases safely and keeping them easy to understand and change over time. Topics include design principles such as Single Responsibility, Open Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion, removing duplication, establishing appropriate abstraction boundaries, separation of concerns, identifying and remediating code smells, incremental refactoring approaches, regression risk mitigation via tests and feature toggles, backward compatibility and migration strategies, and prioritizing technical debt reduction. Interviewers assess the candidate ability to plan pragmatic refactors, minimize risk during change, and improve long term health of a codebase.

MediumTechnical

82 practiced

How would you estimate effort and risk to refactor a complex module of ~5000 lines with many callers? List concrete metrics you'd gather (e.g., cyclomatic complexity, coupling, callers), the process to build an estimate, and how you'd express uncertainty to stakeholders.

EasyTechnical

62 practiced

Describe feature toggles (feature flags) and how you would use them to enable incremental refactors in production. Cover common toggle types, lifecycle (creation to cleanup), naming conventions, ownership, TTL policies, and safety practices to avoid toggles becoming technical debt.

MediumTechnical

66 practiced

A public REST API with many external clients needs to evolve the response payload shape without breaking clients. Propose an API versioning and deprecation strategy (URI versioning, header versioning, content negotiation, semantic versioning) that balances backward compatibility, developer experience, and migration cost. Include rollout steps and monitoring.

MediumTechnical

67 practiced

You inherit a large legacy repository with little to no automated tests. As the Solutions Architect, design a phased plan to introduce unit tests and consumer-driven contract tests across teams to enable safe refactors. Include priorities, safe first targets, CI integration, and success metrics you would track.

EasyTechnical

89 practiced

As a Solutions Architect, how would you advise a product manager and engineering lead to prioritize small technical-debt items in a sprint backlog when deadlines are tight? Provide a repeatable prioritization heuristic and an example of a small trade-off you might recommend.

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