This content is based on a talk that my colleague Tim Kelly and I presented at DevNexus 2026 in Atlanta, one of the largest Java conferences in the world.

Imagine you’re at a supermarket or shopping online. You tap your card or click “Buy Now”. In that exact moment, your bank has to make a decision: is this transaction legitimate, or is it fraud? And it has to do that in milliseconds, and get it right. If it blocks a real transaction, it frustrates the customer. If it approves a fraudulent one, it leads to financial loss. So the question is: how do banks actually do this? What’s happening behind the scenes?…