Instagram

Func req

1. Store / get images

2. Like + comment for image

3. Follow someone

4. Publish (generate) a news feed

NFR

10 mill users monthly MAU

2 photos per month

5MB each photo

10^7 users * 2 photo * 5 Mb = 100.000.000 Mb = 100TB per month (storage) => 1.2 Pb per year