The common pattern is a microservice that connects to the existing payment pipeline through APIs, leaving the pipeline in place.

The sequence that works starts with one measurable use case and a baseline of the current metrics. Next comes a data audit, checking whether transaction records exist at event level with outcome labels. The model then runs in shadow mode against live production traffic for a full seasonality cycle before it takes any real decision, and rollout goes by traffic share with a rules-only fallback retained.