Url trip

http://igoro.com/archive/what-really-happens-when-you-navigate-to-a-url/

Building a Scalable and Resilient Architecture

https://www.javacodegeeks.com/2015/07/building-a-scalable-and-resilient-architecture.html

Doubts about quality of db solution. No relations, no transactions.

Shard

https://en.m.wikipedia.org/wiki/Shard_(database_architecture)