A Custom XCom Backend allows you to redefine how Airflow saves and fetches XCom data. Instead of writing payloads to PostgreSQL, Airflow writes data to cloud object storage (like AWS S3, Google Cloud Storage, or Azure Blob Storage) and saves only the URI/reference path string in the metadata database. Architectural Workflow of a Custom Backend

: Every XCom is uniquely identified by its dag_id , task_id , run_id , and a specific key .

This comprehensive guide covers everything you need to know about Apache Airflow XComs (Cross-Communications). It explores how they work under the hood, standard usage patterns, security considerations, and advanced custom backends. What is an Airflow XCom?