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

SeniorPrefer not to say
Apr 2026

Summary

System design round at OpenAI for a software engineering role, and they threw a full Xiangqi game implementation at me. Not what I expected but in hindsight it makes sense given the complexity they're after.

Questions Asked (1)

Q1

Design and implement an online Xiangqi (Chinese Chess) game, covering board representation, piece movement rules, move validation, game state management, and a basic networking layer for multiplayer.

System DesignTechnical Trade-offsAlgorithms & Data Structures
Author's notes

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scope, then walk through a layered architecture: board representation, move generation/validation, game state management, and networking. Emphasize trade-offs and justify choices based on constraints like latency, consistency, and scalability.

Pro tip: Proactively discuss how you would handle disconnections, reconnections, and cheat prevention, as these are often overlooked but critical for a robust multiplayer game.

1. Clarify Requirements and Scope

Ask about expected scale (concurrent games, players), latency requirements, platform (web/mobile), and whether features like matchmaking, chat, or persistence are needed.

2. Design Board Representation and Move Validation

Choose a data structure (e.g., 2D array or bitboards) and implement piece movement rules with validation, considering efficiency and ease of debugging.

3. Manage Game State and Synchronization

Define game state (board, turn, move history) and decide on authoritative server vs. peer-to-peer, ensuring consistency and handling edge cases like checkmate.

4. Design Networking Layer

Select a protocol (WebSocket for real-time) and design message formats for moves, game events, and state updates, addressing reliability and ordering.

5. Address Scalability and Fault Tolerance

Discuss scaling with multiple game servers, load balancing, and handling failures (e.g., server crashes, network partitions) with reconnection logic.

Key Points to Mention

  • Board representation: 2D array vs. bitboards, with trade-offs in memory and speed.
  • Move validation: implementing piece-specific rules (e.g., horse blocking, elephant river restriction) and check detection.
  • Game state management: turn tracking, move history, and win/loss conditions (checkmate, stalemate).
  • Networking: using WebSockets for real-time communication, with JSON or binary messages.
  • Consistency: authoritative server model to prevent cheating and ensure fair play.
  • Scalability: horizontal scaling with stateless servers and external session storage (e.g., Redis).

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