For CF that I need to perform range scans on, I create separate CF that have custom ordering.
Say a CF holds comments on a story (like comments on a reddit or digg story post) So if I need to order comments by votes, it seems I have to re-index every time someone votes on a comment (or batch it every x minutes). Right now I think I have to pull all the comments into memory, then sort by votes, then re-write the index. Are there any best-practises for this type of index?