Design a scalable image-based social network
Company: Amazon
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
Design the backend system for a social networking website primarily focused on sharing images (similar in spirit to an image-centric social app).
Users should be able to:
- Sign up, log in, and manage a profile.
- Upload images (with optional captions).
- Follow/unfollow other users.
- View a **feed** of images posted by accounts they follow.
- Like and comment on images.
The interviewer specifically cares about how your design will handle **foreseeable, large-scale user growth**: potentially tens of millions of users, high write traffic for uploads and interactions, and very high read traffic for feeds.
**Tasks**
1. Clarify and state the key **functional** and **non-functional** requirements (e.g., latency, availability, consistency, durability).
2. Propose a **high-level architecture**, including major components/services (e.g., API gateway, user service, post/media service, feed service, databases, cache, object storage, CDN).
3. Design how **image upload and retrieval** works end-to-end.
4. Design how a user's **home feed** is generated and served efficiently at scale.
5. Explain how you will **scale the system** as the number of users and operations increases, including:
- Horizontal scaling of stateless services.
- Database sharding/replication strategies.
- Caching and CDN usage.
- Asynchronous processing and message queues.
6. Discuss key **trade-offs** (e.g., push vs. pull feed generation, consistency vs. latency) and how your choices handle high load and growth.
You can assume a cloud environment (object storage, managed databases, load balancers, etc.) is available.
Quick Answer: This question evaluates a candidate's ability to design large-scale backend architectures, covering distributed systems, storage and media handling, caching and CDN strategies, API design, data consistency, and scalability under high read/write workloads.
