https://www.youtube.com/watch?v=VJpfO6KdyWE&ab_channel=Exponent

Functional Requirements

1. Upload/download/view images from a client (mobile/web)
2. Users follow other users.
3. Generate a feed of images.
4. Scale: 10 million users.

Other:

1. search based on titles

Non-functional requirements

1. AP
2. Latency:
   1. For poster: low. <500ms.
   2. For reader: medium. 5s.
3. Highly reliable. Redundancy.

Estimation

• 10M MAU. 1e7
• 2 photos per month per user, on average.
• Each image: 5MB. Image + metadata

Storage: 1e7 * 2 * 5MB / mo = 1e8 MB / mo = 100 TB / mo = 1.2 PB / year