Ask HN: Good cloud storage solution for user data

I am nearing completion of my application. I need cloud storage for my user data. Since I will charge my users for storage + processing, I am looking for a top quality service provider and am not interested in free offers.

The mode of working is: user <--> backend <--> storage.

My main requirements are service uptime and data fidelity (by that I mean data must not get corrupted; what I put I must get back). Backup storage is optional. Encryption is unimportant since my backend anyway encrypts all the data.