We spent way longer on the time complexity discussion than I expected.
Start by clarifying the requirements and scope of the undo system, then propose a design using the Command pattern with a stack-based history. Discuss implementation details, trade-offs, and potential optimizations, and be prepared to write code for core operations.
Pro tip: Demonstrate awareness of real-world constraints like memory usage, concurrency, and persistence, and suggest how Netflix's scale might influence design choices (e.g., distributed undo).
Ask questions to understand the scope: What operations need undo? Is redo required? What are the performance and memory constraints? Is persistence needed?
Propose using the Command pattern to encapsulate operations as objects with execute and undo methods. Use a stack to manage history for undo/redo.
Outline or code the undo and redo methods, handling edge cases like empty stacks. Discuss how to manage command objects and memory.
Compare approaches (e.g., command pattern vs. memento), address memory management (e.g., limiting history size), and consider concurrency and persistence.
If relevant, discuss how the design would change for distributed systems, such as using event sourcing or a centralized undo service.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.