Aims to provide a future proof storage.
There are multiple types of stores, for example Bytes32sStore, BoolsStore if you need all in one you can use contracts/EternalStore.sol.
There is also a managed eternal store where you have ability to disable people from using certain methods and / or keys.
Since the Eternal Storage standard has not been decided yet I am using this for my own projects.
Here is the eternal storage standard if you want to check it out.