**XCom**: Cross-communication—tasks pass small data (e.g., file path, ID). Push via return value or xcom_push(); pull via xcom_pull(). Stored in metadata DB. **Limitation**: Not for large data—metadata DB is not a store. Typical limit ~1 KB per value (configurable but not recommended to increase). **Use**: Pass S3 paths, query IDs, status codes. **Best practice**: Pass references, not payloads. For large data, use external storage (S3, DB) and pass reference....
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