Explain OOP design and API rollout

Quick Overview

This question evaluates object-oriented design and API release engineering competencies, covering identification of core domain objects, separation of orchestration from business rules, testability and extensibility of backend logic, and safe modification of public APIs including backward compatibility, versioning, testing, rollout, monitoring, and client communication, and it is categorized under Software Engineering Fundamentals. It is commonly asked because employers need assurance that engineers can both conceptually design maintainable, extensible systems and practically apply release processes and testing strategies to evolve public interfaces without disrupting clients.

Explain OOP design and API rollout

Company: Microsoft

Role: Software Engineer

Category: Software Engineering Fundamentals

Difficulty: hard

Interview Round: Technical Screen

In one interview round, the discussion focused on practical backend engineering rather than pure algorithms. Discuss both of the following: 1. You are asked to implement a new piece of business logic for an existing backend service using object-oriented design. How would you identify the core domain objects, define responsibilities, separate orchestration from business rules, and make the implementation testable and extensible? 2. You need to modify an existing public API that is already used by clients. What release process would you follow to ship the change safely? Cover backward compatibility, versioning, testing, rollout, monitoring, and communication with clients.

Quick Answer: This question evaluates object-oriented design and API release engineering competencies, covering identification of core domain objects, separation of orchestration from business rules, testability and extensibility of backend logic, and safe modification of public APIs including backward compatibility, versioning, testing, rollout, monitoring, and client communication, and it is categorized under Software Engineering Fundamentals. It is commonly asked because employers need assurance that engineers can both conceptually design maintainable, extensible systems and practically apply release processes and testing strategies to evolve public interfaces without disrupting clients.

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Apr 7, 2026, 12:00 AM
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In one interview round, the discussion focused on practical backend engineering rather than pure algorithms.

Discuss both of the following:

  1. You are asked to implement a new piece of business logic for an existing backend service using object-oriented design. How would you identify the core domain objects, define responsibilities, separate orchestration from business rules, and make the implementation testable and extensible?
  2. You need to modify an existing public API that is already used by clients. What release process would you follow to ship the change safely? Cover backward compatibility, versioning, testing, rollout, monitoring, and communication with clients.
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