Police the prediction-time boundary
Detect and remove data leakage by separating information available before prediction from information known after the outcome.
The move: draw a hard line at prediction time. Table availability is not enough A column can exist in the data warehouse because it is backfilled after the fact. The model can use it only if the live system has it before the decision. Split before learning transforms Feature selection, imputers, scalers, and encoders must learn from training data only. Otherwise the test set influences the training recipe. Watch aggregated features Last 30 days sounds safe only if the 30 days end before the score timestamp, not before the extraction date.
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