Concepts that apply to most Databases - KeynesYouDigIt/Knowledge GitHub Wiki
Really, the first question when working with new OR existing databases is, How Structured is your data?
Replication & Partitioning
When a data set has to be distributed across multiple nodes (usually this means "computers"), things get dicey. And alot more fast and fun!
https://github.com/KeynesYouDigIt/Knowledge/wiki/2.5-Replication
https://github.com/KeynesYouDigIt/Knowledge/wiki/2.6-Partitioning