Yes, this does require that users are online at least once per month for safety.
I wouldn’t call ArcPay a rollup because the state can’t be recreated with on-chain data, that’s why I call it a validium. But it’s very different from any plasma I’ve seen, because plasmas seem to be fully fledged blockchains with their own P2P networks.
There are two major differences between ArcPay and Plasma Snapp as I see it:
- In Plasma Snapp, you have to online at least once a week, and that corresponds to an exit delay of one week. In ArcPay, the online period only corresponds to the exit delay during shutdown - there is no exit delay during normal operation.
- In Plasma Snapp, it looks like we’re assuming that there is a whole P2P network of nodes who are regularly downloading the whole state of the chain. Otherwise the mechanism of rolling back the chain and appointing the new operator would not work. Moreover, the is no mechanism to exit the chain if no one can recreate the state at any point.
Whereas in ArcPay, the entire state is only ever stored by a single operator, and there is no duplication except that each user stores their own Merkle proofs, and we can exit even if the state is not recreated.