This question is basically a marathon disguised as a single prompt.
Start by clarifying functional and non-functional requirements, then estimate scale (users, QPS, storage). Design the core data model and APIs, then dive into feed generation (fan-out on write vs read), storage choices, and trade-offs, ensuring scalability and low latency.
Pro tip: Explicitly discuss the trade-offs between fan-out on write and fan-out on read, and propose a hybrid approach for celebrity users. This shows you understand real-world constraints and can balance competing priorities.
Ask questions to understand functional needs (posting, feed, comments, likes) and non-functional needs (latency, availability, consistency). Estimate scale: daily active users, posts per user, read/write ratio, and storage growth.
Outline core entities (User, Post, Comment, Like, Follow) and their relationships. Specify key APIs for posting, fetching feed, commenting, and liking, including pagination and rate limiting.
Sketch components: clients, API gateway, services (post, feed, comment, like), databases (SQL/NoSQL), cache, message queue, and CDN. Explain data flow for each operation.
Compare fan-out on write vs fan-out on read, discussing pros/cons. Propose a hybrid approach for scalability, and detail how to handle ranking, pagination, and real-time updates.
Discuss sharding, replication, caching strategies, consistency models, and failure handling. Highlight trade-offs made and how they align with requirements.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.