| > […] my bank warning me about credit and debit card unavailability […] Your bank might have meant card balances being unavailable in the online banking which is more plausible than cards being generally unavailable for payments. It is not indicative of the mainframe actually being down (although not entirely improbable, either), and it is more likely that an intermediary (a service or a server) was undergoing maintenance. Payment processing involves multiple tiers and multiple routing layers built into it – to ensure very high availability and that a payment is almost always guaranteed to process (successfully or otherwise – does not matter). Payment networks also impose stringent technical requirements onto the banks connecting to them. A Raspberry Pi running Slackware Linux from 1993 and powered by a dangling street pole wire would not be allowed to connect, for example. Your bank (or mine, for the sake of the conversation) is the terminal point in this whole payment processing chain, with the payment network (Visa, Mastercard but not AmEx[0]) being the port of entry for a payment. Depending on the country, a country may have its own local payment Visa / MC processing centre and if that is the case, local payments will be routed to the local card payment processor. Otherwise, a global Visa/Mastercard will assume the payment. Then the payment network contacts your local bank to authorise the payment. Depending on the nature of the failure + other factors, the Visa/Mastercard can authorise certain payments on behalf of your bank if they fail to reach your bank and will forward the payment particulars onto your bank so that your bank could correctly process your card payment later. It is more common in overseas payment scenarios, i.e. you are travelling overseas and especially so when travelling outside the first world countries. Payment networks and banks do not like such situations and actively loathe non-real time payment authorisations, yet they allow them for a narrow number of use cases at their own discretion. [0] AmEx own their own global payment network and do not allow other financial institutions to gain access into it. |