Design coding platform leaderboard system

Q: Design coding platform leaderboard system

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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Question

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.

Design coding platform leaderboard system

System Design: Scalable Coding Platform with Live Global Leaderboard

Context

Requirements

Solution

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