The decision
A noul question, "this transaction needs review", over a state built from the transaction and a short account history. It is written as text or JSON: amounts, countries, merchant category, device changes and recent velocity.
How to build it
- Export past transactions with their investigation outcomes. Those are your labels.
- Fine-tune Laya on them in System One Studio (
systemone run studio). It scores the fine-tune against the base on held-out rows before you ship. - Serve it next to your payment flow, and send everything above your threshold to the analyst queue.
- Watch precision at the threshold weekly. Fraud patterns drift.
Make it better
Keep a rules engine for the hard constraints, such as sanctions and amount limits, and use the model for the grey zone the rules can't describe.