Simple measures created from facts can use these types of aggregations.
export type MeasureAggregation = "sum" | "count" | "approximate_count" | "avg" | "min" | "max" | "median" | "runsum";
Note the special approximate_count aggregation. It translates to corresponding SQL function on backend if the underlying data source supports it. Otherwise the backend should fall back to classic exact count. Some backends are oblivious to this functionality completely - for them it's ok to perform the fallback already in SDK backend.