In finance it can be critical. Some tasks actually require absolute granularity, up to 6 decimal places of precision and thereafter reliance on atomic order of

In finance it can be critical. Some tasks actually require absolute granularity, up to 6 decimal places of precision and thereafter reliance on atomic order of arrival, for deterministic results on data from high frequency trading. Without absolute knowledge of the order or if there's aggregation the best you can do is approximate, which often is considered suboptimal when the real solution is available.