Comment by alphaoide

This was recommended in a blog post I read. I haven't read it myself but the table of content looks promising

https://www.educative.io/collection/5668639101419520/5649050...

Designing a URL Shortening service like TinyURL

Designing Pastebin

Designing Instagram

Designing Dropbox

...

Key Characteristics of Distributed Systems

Load Balancing

Caching

Sharding or Data Partitioning

...