For a production app you will need your own cloudDB / redis Server (you cannot rely on/and should not use the MIT provided one, it is only for developing/testing). Therefore storage capacity and performance is all down to how much you are prepared to pay, or how quick and good your own server is if you setup your own redis server. Be aware that many of the big providers of redis servers may not have the correct setup to work with SSL, using the MIT provided cloudDB components.
For your own server:
HOWTO: Setup Redis Server with SSL for use with AI2
I do hope this answer is "right now" enough for you 