About CACHING : ---
To avoid expensive re-acquisition of resources by not releasing
the resources immediately after their use. The resources retain their identity, are kept in some
fast-access storage, and are re-used to avoid having to acquire them again.
![alt text](./etc/caching.png "Caching")
Use the Caching pattern(s) when
* Repetitious acquisition, initialization, and release of the same resource causes unnecessary performance overhead.
* [Write-through, write-around, write-back: Cache explained](http://www.computerweekly.com/feature/Write-through-write-around-write-back-Cache-explained)
* [Read-Through, Write-Through, Write-Behind, and Refresh-Ahead Caching](https://docs.oracle.com/cd/E15357_01/coh.360/e15723/cache_rtwtwbra.htm#COHDG5177)