You have two built-in options for Data and then you could also bring your own db into the mix if needed.
The two built-in options are accessed via the State and File libraries.
State is a key value store meant for short term data storage. keys inserted have a limited time before they are flushed from the store. You can tune this time by setting the TTL value. If you set the TTL value to -1 it will last forever.
File allows you to store files. You can use this to either many data files or a single file with json data in it.
App Builder Docs - Dealing with data
