Design Instagram
Design a photo-sharing app where users upload photos, follow others and scroll a home feed.
Photo sharing social network · Medium
Functional requirements
- Upload photos with captions
- Follow and unfollow users
- Home feed of followed users' posts
- Like and comment
Scale & non-functional requirements
- 500M daily active users
- Feed loads in under 200 ms
- Photos are never lost
Hints
- Fan-out on write vs fan-out on read for the feed?
- How are images stored and served globally?
- What happens for celebrities with 100M followers?