Comment by Animats

> That's true, but it doesn't help the customers.

Sure it does. It's essential to making banking work. See ISO 20022 reconcilation.[1] This is the process by which errors in money transactions between banks are resolved. ISO 20022 is used by SWIFT, FedNow, FedWire, and systems in about 70 countries.

Unique IDs make transactions idempotent, but that's just the start. Banking is an eventually consistent system. Messages go back and forth until both ends agree. If there's a loss of communication, some transactions will be resubmitted, but they won't be applied twice.

Banks have been doing reconciliation for centuries. It's been sped up recently, but the concepts have not changed much.

[1] https://www.finextra.com/blogposting/19808/how-exactly-will-...