Pretty well-trodden territory if you've done any system design prep.
Start by clarifying requirements and scale (e.g., number of users, submissions per day), then outline core features like problem browsing, code submission, and judging. Propose a high-level architecture with clear separation of concerns, and dive into 1-2 critical components (e.g., code execution sandbox, real-time submission processing) discussing trade-offs.
Pro tip: Emphasize security and isolation in the code execution environment, as it's the most challenging part; mention using containerization (Docker) with resource limits and network isolation, and discuss how to handle untrusted code safely.
Ask questions to understand expected scale (users, submissions), core features (problem set, code editor, judge, contests), and non-functional requirements (latency, security, availability).
List essential features: problem browsing/search, code submission, real-time judging, user profiles, leaderboards, and contests. Describe the main user flow from problem selection to submission and feedback.
Sketch a microservices-based architecture with components: API gateway, user service, problem service, submission service, judge service, and database. Explain data flow and interactions.
Focus on the code execution sandbox: how to run untrusted code securely using containers, resource limits, and queuing. Discuss scalability of the judge service with message queues and worker pools.
Address trade-offs: SQL vs NoSQL for problems/submissions, synchronous vs asynchronous judging, caching strategies, and how to scale horizontally. Mention monitoring and fault tolerance.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
This came as a follow-up and I fumbled it a bit.
Start by explaining the mechanics of signed URLs: a server generates a URL with a cryptographic signature that grants temporary access to a specific resource. Then, connect it to Whatnot's context by discussing use cases like live stream video delivery, user-uploaded images, or order invoices, emphasizing security and scalability benefits. Finally, outline when to use them—such as for direct client uploads/downloads—and mention trade-offs like expiration and revocation.
Pro tip: Mention that signed URLs offload traffic from your servers and reduce costs, but also highlight the importance of setting short expirations and using HTTPS to prevent leaks. This shows you consider both performance and security.
Explain that a signed URL contains a cryptographic signature (e.g., HMAC) and an expiration time, allowing temporary access to a private resource without requiring authentication credentials.
Describe the process: the server generates a URL with a signature based on the resource path, expiration, and a secret key; the client uses it to access the resource directly from storage (e.g., S3, GCS).
Discuss scenarios like serving live stream video segments to viewers, allowing sellers to upload product images directly to cloud storage, or providing temporary access to order invoices.
Highlight benefits: reduced server load, improved scalability, and enhanced security. Mention trade-offs: expiration management, inability to revoke easily, and potential for URL sharing.
Summarize best practices: use short expirations, restrict by IP if possible, use HTTPS, and monitor for abuse. Tie back to system design goals like scalability and security.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Start by clarifying the requirements and scale (e.g., number of concurrent users, expected latency, read/write patterns). Then propose a high-level architecture that addresses scalability, focusing on real-time communication, data consistency, and fault tolerance. Finally, dive into specific components and trade-offs, showing awareness of bottlenecks and mitigation strategies.
Pro tip: Emphasize the importance of load testing and gradual rollout to validate scalability assumptions, and mention how you would monitor key metrics like latency, error rates, and resource utilization in production.
Ask questions to understand the expected number of concurrent users, peak load, latency requirements, and read/write ratio. This ensures your design targets the right scale and constraints.
Outline a scalable architecture using load balancers, stateless services, and a pub/sub system for real-time updates. Consider using WebSockets or server-sent events for live interactions.
Choose appropriate databases (e.g., NoSQL for scalability, SQL for transactions) and discuss sharding, replication, and caching. Address how to handle consistency for live scores and leaderboards.
Explain horizontal scaling of services, auto-scaling groups, and partitioning strategies. Discuss redundancy, failover, and graceful degradation to handle failures.
Describe how you would monitor the system (metrics, logging, tracing) and use load testing to validate scalability. Mention iterative improvements based on real-world data.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.