Yeah, the idea in the above code is that you can't do anything with an account so long as it's placed in the "blocked" set, because that means that it's effecti

Yeah, the idea in the above code is that you can't do anything with an account so long as it's placed in the "blocked" set, because that means that it's effectively taken out of circulation for other operations. The way I solve situations like this is, by making sure that all accounts are moved to the same thread for a short period of time, which then handles the transaction. Which I find a lot easier to think about. It's essentially sharding by account and flexibly moving the shards into the same single writer context. But if you want to do things the "old fashioned way" Rust provides plenty of classical synchronisation primitives like `Mutex` or `RwLock`. You can also combine both approaches, e.g. have a single Mutex<AccountPool> that you can check out accounts from.