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

SeniorPrefer not to say

Jun 2026

Summary

System design round at Microsoft for a software engineer role. One big open-ended question about building a chess platform, and they really did want you to go deep on all of it.

Questions Asked (1)

Design an online chess platform similar to chess.com, covering matchmaking, real-time gameplay, multiple time controls, spectating, post-game analysis, ratings, puzzles, and tournaments.

System DesignTechnical Trade-offs

Author's notes

This question is basically a full system design in one prompt.

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AI HintsAI Generated

Suggested Approach

Start by clarifying functional and non-functional requirements, then focus on the core real-time gameplay and matchmaking components before addressing secondary features like puzzles and tournaments. Emphasize scalability, low-latency, and consistency trade-offs, and discuss how you would evolve the design from MVP to full-featured platform.

Pro tip: Demonstrate awareness of the unique challenges of real-time chess, such as clock synchronization and move validation, and propose using WebSockets with a stateful game server per match. Also, mention how you would handle cheat detection and fair play, which is critical for a competitive platform.

1. Clarify Requirements and Scope

Ask questions to understand expected scale (concurrent users, games per second), latency requirements, and which features are must-have vs. nice-to-have. Define functional requirements (matchmaking, gameplay, spectating, etc.) and non-functional requirements (availability, consistency, latency).

2. High-Level Architecture

Sketch the main components: client apps, API gateway, matchmaking service, game servers, database, cache, message queue, and analytics. Choose appropriate technologies (e.g., WebSockets for real-time, Redis for matchmaking queues, Cassandra for game history).

3. Deep Dive into Core Components

Detail matchmaking (ELO-based pairing, time control buckets), real-time gameplay (move validation, clock sync, state persistence), and spectating (fan-out, delayed streams). Discuss data models for games, moves, and ratings.

4. Address Scalability and Reliability

Explain how to scale horizontally (sharding game servers, partitioning matchmaking by region/time control), handle failures (game server crashes, reconnection), and ensure low latency globally (edge servers, regional deployments).

5. Cover Secondary Features and Trade-offs

Briefly cover post-game analysis (stockfish integration, async processing), puzzles (precomputed positions, rating system), and tournaments (scheduling, brackets). Discuss trade-offs like consistency vs. availability, and cost vs. performance.

Key Points to Mention

Matchmaking algorithm: ELO/ Glicko rating system, time control buckets, and expanding search range over time.
Real-time communication: WebSockets for bidirectional low-latency communication, with fallback to long polling.
Game state management: Authoritative server for move validation, clock synchronization using server time, and persistence of moves for replay.
Scalability: Sharding game servers by game ID, using Redis for matchmaking queues, and CDN for static assets.
Spectating: Pub/sub model to broadcast moves to spectators, with options for delayed streams to prevent cheating.
Post-game analysis: Asynchronous processing with chess engines (e.g., Stockfish) and caching of analysis results.

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