Design coding platform leaderboard system
Overview
This question evaluates system design and distributed-systems skills, including scalable execution orchestration, secure sandboxing of untrusted code, test-case storage/distribution, message-queue resilience, and low-latency real-time leaderboard updates.
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Jul 29, 2025, 8:05 AM
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System Design
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System Design: Scalable Coding Platform with Live Global Leaderboard
Context
Design a coding challenge platform (similar to LeetCode) where users submit code to be compiled and executed against test cases at scale. The system must provide a live global leaderboard that updates in near real time.
Assume:
- Millions of users, with peak submission bursts (e.g., during contests).
- Multiple languages/runtimes (e.g., Python, Java, C++), each with time/memory limits.
- Hidden and public test cases; hidden cases must never be leaked to clients.
- Fairness and isolation: untrusted user code must run in sandboxed environments.
Requirements
Design the system to address:
- Test-case storage and distribution to executors.
- Execution orchestration (compile, run, shard across test cases, aggregate results).
- Message-queue fault tolerance (retries, idempotency, DLQs, ordering where needed).
- Scalability and elasticity across services.
- Live global leaderboard with low-latency updates.
Call out key APIs, data models, high-level architecture, and operational considerations.
Solution
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