The last 12 months I have collaborated on a real time fraud monitoring engine at BNP Paribas Fortis.
David Massart (cfr http://de-solution.com) has made a nice presentation on how it works at the Bay Area Flink Meetup of Sep 24th 2019:
https://www.slideshare.net/slideshow/embed_code/key/ayhMH7XmvO6E33
He had already done a previous presentation in 2018 that you can see iton youtube: