Reviewed by Aditya Kumar · Last reviewed 2026-03-24
**What**: XComs (Cross-Communication) in Airflow enable task-to-task data passing. Push via xcom_push() or return; pull via xcom_pull(). **Why**: Pass small metadata—file paths, counts, task IDs. NOT for large payloads—use S3/GCS and pass paths. **Backend**: DB default; custom...
What: XComs (Cross-Communication) in Airflow enable task-to-task data passing. Push via xcom_push() or return; pull via xcom_pull().
Why: Pass small metadata—file paths, counts, task IDs. NOT for large payloads—use S3/GCS and pass paths.
Backend: DB default; custom (S3, Redis) for scale. TaskFlow API in Airflow 2.0+ returns values directly.
Trade-off: Large payloads in XCom strain metadata DB; keep serializable, small.
Red Flag: Passing 1MB payload via XCom. Pro-Move: 'We pass S3 paths only; metadata DB stays lean.'
According to DataEngPrep.tech, this is one of the most frequently asked General/Other interview questions, reported at 1 company. DataEngPrep.tech maintains an editor-reviewed database of 1,863 data engineering interview questions across 7 categories.