Yes, there is some backend code to support sync between devices and moving data from one device to another. I don't plan to have a big backend code base, it's a bit of outside of my expertise.
Oh, may be I misunderstand you. So far it was ~1500 users per day which is quite small amount considering I don't need to store any big amounts of data. I pay for server and domain myself, I can afford it and don't think it can be overloaded in the near feature.