The Amazon Web Service outage that started around 1pm August 23 local Japan time took down some PayPay service along with it. Japanese users tweeted about payment and recharge not working. AWS service was completely restored by 8pm Japan time. Engadget JP’s Takahiro Koguchi posted a complete rundown.
Since QR Code payment systems depend on centralized processing, a cloud outage can easily bring down the system for all transactions. While this is a minor annoyance for paying at a convenience store where you can always pay on the spot using something else, it’s not the case when QR is used for transit where large numbers of people can suddenly be stranded. This is exactly what happened in Chengdu last April. It’s a risk of using QR Codes for transit.
Locally processed transactions like Suica are resilient because it was designed to avoid the trap of central processing, the stored balance is held on the card and not on the cloud. When things do go wrong with cloud services like Mobile Suica or Apple Pay, damage is limited to the credit card recharge side. Cash recharge at the convenience store, the station, the ATM is always there as a backup because it only deals with the card, not the cloud.