Persistant Storage API

Hi,

I want to store custom data on application level and user level.

I saw one article on it.

https://community.lithium.com/t5/Product-Ideas/Persistant-Storage-API/idi-p/61444

As per article user field have some custom data field which can we use it but i can't find anything more.

Suggest a way to store custom data on application level and user level.