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Shopify·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Apr 2026Remote

Summary

Shopify had me build a Mars rover controller from scratch in an empty Git repo. The requirements were deliberately vague, which was either a clever design choice or mildly frustrating depending on your mood. Pretty classic systems-thinking exercise dressed up as a fun space problem.

Questions Asked (1)

Q1

Build a Mars rover controller from an empty Git repository. The rover starts at (0,0) facing north and must support turn_left, turn_right, and move commands, reporting position and direction after each command. Requirements are intentionally underspecified.

Adaptability & AmbiguitySystem DesignTechnical Trade-offs
Author's notes

The underspecified part is where I spent most of my mental energy.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements and constraints with the interviewer, then outline a simple, extensible design before coding. Implement the core functionality incrementally, testing each command, and be prepared to discuss trade-offs and potential extensions.

Pro tip: Demonstrate adaptability by acknowledging the ambiguity and proposing a minimal viable solution first, then iterating based on feedback. This shows you can deliver value quickly while remaining open to change.

1. Clarify Requirements

Ask questions to understand the expected behavior, edge cases, and constraints. For example, confirm the coordinate system, command input format, and whether the rover can move off the grid.

2. Design the Solution

Sketch a simple design: a Rover class with position (x, y) and direction (N, E, S, W), and methods for turn_left, turn_right, and move. Consider using an enum for directions and a mapping for turns.

3. Implement Incrementally

Code the basic functionality first, then add tests or manual verification. Start with initialization, then implement each command, ensuring correct state updates.

4. Test and Validate

Run through example command sequences to verify correctness. Discuss how you would handle invalid commands or boundary conditions.

5. Discuss Extensions and Trade-offs

Talk about potential extensions like obstacles, multiple rovers, or a command parser. Mention trade-offs between simplicity and extensibility, and how you would refactor if requirements change.

Key Points to Mention

  • Importance of clarifying ambiguous requirements before coding
  • Choice of data structures (e.g., enum for direction, tuple for position)
  • Handling of edge cases such as invalid commands or moving off the grid
  • Testing strategy (unit tests, manual testing, or property-based testing)
  • Design principles like separation of concerns and extensibility
  • Communication and collaboration with the interviewer throughout the process

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