I have a question about active replication and ordering. I am aware that traditionally active replication in a distributed system requires total ordering to propagate requests to replicas, however, I have thought of an example where may this wouldn't be necessary.
Picture a bank account system using active replication. But instead of being able to debit your account, you can only credit your account (so only add positive amounts to your balance). Does the banking system need ordering guarantees then? Considering if I were to add £5 then £10 to my account, if the replicas did not receive this in order, it would still amount to £15 regardless of the order they have received the request in. There's no real conflicts that could arise for ordering, a part from the fact the user may be a bit annoyed to see that their account only has £5 in it when they credit £10 first. But more technically, where is the problem?
I imagine I'm wrong, but can't really see why. Would someone be able to explain to me in a bit more detail?