Design an online coding platform

Design an online coding practice and interview platform (similar to well-known coding challenge sites). The platform should allow: - Users to sign up, log in, and manage profiles. - Users to browse, search, and filter coding problems. - Users to write, run, and submit code solutions in multiple programming languages through a web-based editor. - Automatic judging of submissions against hidden test cases, with results (e.g., Accepted, Wrong Answer, Time Limit Exceeded). - Tracking of user statistics and progress (e.g., solved problems, difficulty distribution). **Requirements and considerations:** 1. **Functional requirements** - Problem management: create, update, and categorize coding problems (by difficulty, topic, etc.). - Code execution: run user-submitted code safely and efficiently in isolated environments. - Submissions: store submission history and results per user and per problem. - Ranking/leaderboards: optionally show user rankings. 2. **Non-functional requirements** - High availability and scalability to support millions of users and high QPS during peak times. - Low latency for listing problems and fetching problem details. - Reasonable turnaround time for judging submissions. - Strong isolation and security for untrusted user code. 3. **Constraints (assume)** - Target: 5M registered users, up to 200k daily active users. - Peak: 10k code runs per minute. Describe how you would design this system end-to-end. Talk about: - High-level architecture and major components. - Data modeling and storage choices. - Code execution and sandboxing, including how to scale the judge/execution layer. - Handling of traffic patterns, caching, and performance optimizations. - Key trade-offs and how you would evolve the design as traffic grows.