Astronomer - Apache Airflow 3 Fundamentals DAG Authoring Study Guide

7: Assets and cross-DAG dependencies

This chapter covers the three cross-DAG coordination mechanisms in Apache Airflow 3, walking through data-driven scheduling with Assets (declaration, producer outlets, consumer schedules, boolean expressions, aliases, the `@asset` decorator, event payloads with `extra`, and asset watchers), the poll-and-wait model of `ExternalTaskSensor` with `execution_delta` and `execution_date_fn`, and the push-based `TriggerDagRunOperator` for programmatic fan-out. The chapter closes on the `schedule=None` trigger-only DAG pattern and the decision framework for selecting the right mechanism for a given cross-DAG use case.