What does it mean to be cluster-friendly in NoSQL? Also, please explain the common characteristics of NoSQL databases

Question

I cannot seem to find much information that explains what exactly cluster-friendly means in NoSQL. I am still relatively new to database management in general even though I've had some experience with MySQL, so I would love someone with the proper knowledge to elaborate this topic to me. The common characteristics among NoSQL databases:

Non-relational
Schema-less
Cluster friendly (not always)
Open source (not always)
came out of the 21st century web (there are other non-relational databases that have been around for decades that are not considered NoSQL)

Answer 1

"Cluster-friendly" means that the database can easily be distributed on lots of machines.

When a relational database reaches its capacity, you can usually just buy a larger server. Distributing the load of one database on multiple servers is possible with some relational databases, but it usually doesn't scale linearly.

Many NoSQL databases, however, are designed with scalability in mind. When one machine becomes too slow, you can usually add more machines to the cluster with minimal effort to improve performance.