Data engineering·Orchestration and running it in anger
the source team changed a status code's meaning, the pipeline kept running, and your funnel report has been wrong since Tuesday.
Upstream drift
Also calledsource drift, silent upstream change
The producing system changing behaviour — semantics, encoding, defaults, volume — without changing anything your pipeline validates. It is worse than a schema break precisely because nothing fails: the types still match and the numbers are merely wrong. The defences are semantic tests rather than structural ones, and a contract with the producer that says which changes require notice.