Amazon·Software Engineer·Onsite - System Design / Architecture·Intermediate

Intermediate

Apr 2026

Summary

Amazon SWE interview with a system design question about building a Tic Tac Toe game that supports remote play. Pretty open-ended, which I wasn't fully prepared for.

Questions Asked (1)

Design a Tic Tac Toe game that supports remote multiplayer play.

System DesignTechnical Trade-offsAPI & Integrations

Author's notes

I jumped straight into the game logic and spent way too long on the board state before they nudged me toward the networking side.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scope (e.g., real-time vs turn-based, matchmaking, persistence, scale). Then outline a high-level architecture covering client, API gateway, game service, state store, and real-time communication, and dive into key components like game state management, concurrency, and scalability. Finally, discuss trade-offs and potential optimizations.

Pro tip: Emphasize idempotency and consistency in game state updates to handle network retries and concurrent moves, which is critical for a fair multiplayer experience.

1. Clarify Requirements

Ask questions to understand functional and non-functional requirements: real-time vs turn-based, number of concurrent games, latency expectations, persistence, matchmaking, and authentication.

2. High-Level Architecture

Sketch the main components: client apps, API gateway, game service (stateless), game state store (e.g., Redis), matchmaking service, and real-time communication (WebSockets or polling).

3. Deep Dive into Key Components

Detail game state management (board representation, move validation), concurrency control (locking, optimistic concurrency), and real-time updates (pub/sub, WebSockets).

4. Scalability and Reliability

Discuss how to scale horizontally, handle failures (retries, idempotency), and ensure low latency (edge servers, caching).

5. Trade-offs and Alternatives

Compare design choices (e.g., WebSockets vs polling, Redis vs DynamoDB) and justify decisions based on requirements.

Key Points to Mention

Game state representation and move validation logic
Real-time communication using WebSockets or long polling
Concurrency control and idempotent move handling
Matchmaking and session management
Data persistence and recovery (e.g., Redis with persistence)
Scalability considerations: sharding, load balancing, and latency optimization

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