Generating test data that changes while it runs: SimPy simulations written with a declarative API that read settings from and write events to PostgreSQL and Redis.

Keeping a simulation in step with live data: change a running SimPy model's parameters from Kafka and stream its events out, so it acts as a digital twin.

Why a simulation is not a digital twin: the layers that separate an offline model, an operational twin and an event-driven hybrid of the two.

An Apache Flink and Kotlin streaming architecture where online machine learning detects concept drift from machinery wear, controlled by a shadow mode router.