The Join That Kills Your Model: How Cardinality Explosions in Production Databases Destroy ML…
A common but often overlooked issue in production ML pipelines is the "cardinality explosion" caused by database schema changes. When tables are normalized or new relationship tables are added, joins can unexpectedly multiply rows, leading to inflated or deflated features. This distortion can cause ML models to make wildly inaccurate predictions, as demonstrated by a revenue prediction model that began forecasting revenues five times higher than reality after a database normalization sprint. The article suggests using synthetic databases to test join cardinality before schema changes impact feature pipelines. AI
IMPACT Highlights a critical failure mode in ML systems, emphasizing the need for robust data validation to ensure model reliability.