I would like to know if there is a way to delete old/unused data easily ?

I know about TTL but there are 2 limitations of TTL:

- AFAIK, there is no TTL on counter columns
- TTL need to be defined at write time, so it's too late for data already inserted.

I also could use a standard "delete" but it seems inappropriate for such a massive.

In some cases, I don't know the row key and would like to delete all the rows starting by, let's say, "1050#..." 

Even better, I understood that columns are always inserted in C* with (name, value, timestamp). So is it possible to delete all the data inserted in some CF between 2 dates or data older than 1 month ?