When calculating consumption by adding consumption of various equipment, we use something like
sum(last_foreach(/host/key/[hostgroupfilter and tagfilter])
This item is calculated periodically taking into account the update interval of the items to be added.
Since the last_foreach function returns the last value harvested, in the event that one or several devices have not recently harvested data, we are going to add values that are not recent, may be hours or days old, obtaining erroneous results.
It would be desirable that it only take relatively recent values, in other words it would be a last, but with a time limit, something like last_newer(15m,0) that returns the value if it occurs in the last 15 minutes or the specified value if there are no values in that time.
When the value is numeric, we use a work around calculating the average of the last 15m (assuming the update interval is 15m)