Apple·Software Engineer·Onsite - System Design / Architecture·Senior

Senior

Jun 2026

Summary

Apple software engineering interview focused entirely on a system design refactor problem. The prompt was deceptively meaty for what felt like a coding round, lots of moving parts to juggle at once.

Questions Asked (1)

You have an existing Rock-Paper-Scissors tournament with three robot players. Refactor it so the number of rounds is configurable, ties are tracked, and the design is extensible for new strategies or gestures. Walk through your class and interface changes and explain how you'd keep it testable.

System DesignTechnical Trade-offs

Author's notes

This one took me a minute to even figure out where to start.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the current design and requirements, then propose a refactor that introduces interfaces for gestures and strategies, a configurable round count, and tie tracking. Emphasize testability through dependency injection and unit tests for each component.

Pro tip: Mention that you'd use the Strategy pattern for player strategies and the Factory pattern for creating gestures, and that you'd write tests first to ensure the refactor doesn't break existing behavior.

1. Clarify Requirements and Current Design

Ask questions to understand the existing codebase, constraints, and what 'extensible' means for the team. Identify the core entities: gestures, players, rounds, and tournament.

2. Identify Abstractions and Interfaces

Define interfaces for Gesture (e.g., beats(other)), PlayerStrategy (e.g., chooseGesture()), and possibly GameRules. This allows new gestures and strategies to be added without modifying existing code.

3. Refactor Tournament Class

Make the number of rounds a constructor parameter. Track ties as a separate counter. Use dependency injection to pass in players and rules, making the class testable.

4. Ensure Testability

Write unit tests for each component: gesture comparisons, strategy behaviors, round counting, tie tracking, and tournament outcomes. Use mocks for strategies to isolate tests.

5. Discuss Trade-offs and Extensibility

Explain how the design supports adding new gestures (e.g., Lizard, Spock) and strategies (e.g., AI, random) without modifying existing code. Mention potential trade-offs like increased complexity.

Key Points to Mention

Use of interfaces (e.g., Gesture, PlayerStrategy) to decouple behavior and enable extensibility.
Dependency injection to make the Tournament class testable and configurable.
Strategy pattern for player decision-making, allowing new strategies to be plugged in.
Factory pattern for creating gestures, so new gestures can be added easily.
Separation of concerns: tournament logic, round management, and tie tracking should be distinct.
Unit testing with mocks to verify interactions and edge cases (e.g., all ties, invalid gestures).

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.