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.

HardTechnical

71 practiced

You're asked to lead a cross-team refactor of a widely used shared library. Describe how you would organize the effort: governance, migration windows, communication plan, owning a deprecation policy, CI safety nets, and assessment of SLO impact across consumers.

HardSystem Design

61 practiced

Design a strategy to refactor a data-access layer in a multi-region service so reads are region-local while maintaining a single logical API for clients. Discuss abstraction boundaries, consistency models, fallbacks, and how to roll out changes without breaking clients.

EasyTechnical

89 practiced

Describe the Open/Closed Principle (OCP) and provide an SRE-focused example: you need to add new remediation strategies to an existing incident-response engine without modifying core evaluation logic. How would you design extensibility while keeping the system stable?

MediumTechnical

66 practiced

During a production incident you find a refactor introduced a silent regression that was not covered by tests. Walk through the incident response and post-incident review steps you would take, focusing on code-level fixes, test improvements, deployment rollbacks, and actions to reduce similar regressions in the future.

MediumTechnical

68 practiced

Explain Dependency Injection (DI) and demonstrate (in prose or pseudo-code) how DI improves testability for an SRE automation script that interacts with a cloud provider API. Show how to inject a mock provider for unit tests and how this avoids flakiness or credentials issues in CI.

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