I suggest that we could make indexedDB more clearly for all alarms information only.
We could use asyncStorage.setItem()/asyncStorage.getItem() to instead of creating another indexedDB.

(Such as Music app, 
https://github.com/mozilla-b2g/gaia/blob/master/apps/music/js/Player.js#L99
https://github.com/mozilla-b2g/gaia/blob/master/apps/music/js/Player.js#L568
https://github.com/mozilla-b2g/gaia/blob/master/apps/music/js/Player.js#L582)
It will need to import the link of "shared/js/async_storage.js". 
(https://github.com/mozilla-b2g/gaia/blob/master/apps/music/index.html#L17)
Then, we don't need to create another indexedDB for a value.