I've never heard of financial systems being eventually consistent, certain not ATMs which need to know your exact balance and how much money you've taken out already today.
I studied ATM's at Uni, and they have been like that for over 26 years.
As someone else on the thread pointed out, they do authenticate you, and record the transaction in a aci(Durable!) database before they give you money. But the system clearly has a degraded mode when the exact balance is unavailable.
Also why do you need a balance to process a deposit?
In most cases when processing a withdrawal, ATMs or POS terminals don't know your exact balance and how much money you've taken out already today. A withdrawal tends to involve a request for $X which gets a yes/no response from the bank or from the chip of the card if the terminal is not online connected - the bank or chipcard logic will check the balance and daily limits, not the ATM.
You can think of the (rare nowadays, but possible) offline, paper-based card transactions (physical imprint of the card number + signature) as a very strong example of eventual consistency - your card will be billed for that amount sometime later when the documents are processed and all the balances will be correct, but for many days the "online visible" card balance as known to the bank will be different from the "real" legal/accounting balance of that card.
I don't know if you've ever travelled but very often withdrawals from an ATM will be processed without the balance of the user being known at that time.
It's why your bank account can go into negative territory.
I studied ATM's at Uni, and they have been like that for over 26 years.
As someone else on the thread pointed out, they do authenticate you, and record the transaction in a aci(Durable!) database before they give you money. But the system clearly has a degraded mode when the exact balance is unavailable.
Also why do you need a balance to process a deposit?