Photo Sharing (Instagram)
Difficulty: Medium
What It Tests
Media storage, CDN, social graph, feed delivery at scale.
Topics Covered
- Blob / Object Storage
- CDN (Content Delivery Network)
- Database Sharding
- Caching
- Fanout Patterns
- Database Design: SQL vs NoSQL
Hello Interview Breakdown
Read the full Hello Interview breakdown →
Approach Hints
- Store photos in S3, serve via CDN
- Shard user and media tables by user_id
- Use fan-out-on-write for feed (pre-build follower feeds)
- Use fan-out-on-read for celebrity accounts to avoid write amplification