It's called Paylah which is an app from our local bank DBS
https://www.dbs.com.sg/personal/deposits/pay-with-ease/paylah-5-million-hawker-meals
apparently too successful which I guess overloaded their servers.
https://sg.finance.yahoo.com/news/dbs-posb-experience-third-service-disruption-in-two-years-074730477.html