Expiring empty cache regions

[fatefree]

I have a very dynamic cache, we cache mq requests by a region and a subregion. There are a finite amount of possible subregions numbering in the thousands, and each element placed in the subregion expires after 30 minutes. I was just concerned because if for example all of the elements in a subregion have expired, the subregion node itself will sit there forever.

I know one option is to have the subregion expire as well, but I don't want the elements inside to expire before their 30 minutes are up so i dont think thats an option. Do you think this is a potential memory concern having these empty nodes sit around?

[manik]

It depends how deep your tree structure is. There is some overhead in having structural nodes sat around unnecessarily, but as long as these don't number in the thousands, you should be ok. At the end of the day, put your data in leaf nodes so they can be cleared up by eviction.