At ShermansTravel, we already tested Cassandra and Tokyo Cabinet/Tokyo Tyrant.  We are starting the implementation phase this week.  The issue with Tokyo Cabinet for us was writes were too slow.  The issue with Cassandra was that reads were a little slower than we'd like, but with some caching (either eventually being built into Cassandra or with memcache in front of it).

We do a lot of mailings and we want to track who received what mailing, what kind of mailing, and that when we segment the lists for mailings (in MySQL), we need to check that the user hasn't received too many mailings of a certain type over a certain period (get_slice).

We are also evaluating a social network usage similar to the way Facebook and Digg use the Like concept.  We want to make recommendations on our site based on what a user's network likes based on location.  We believe (although we haven't started evaluating yet) that Cassandra will be the method of storing/accessing this data as well.

As I mentioned earlier some caching would be nice and also (I believe this was suggested earlier in the thread), a remove_by_slice method.  Also (and I will likely end up writing some of these myself), some Nagios plugins to check the health of Cassandra.

Thanks for the excellent product.

-e

On Fri, Nov 20, 2009 at 4:17 PM, Jonathan Ellis <jbellis@gmail.com> wrote:
Hi all,

I'd love to get a better feel for who is using Cassandra and what kind
of applications it is seeing.  If you are using Cassandra, could you
share what you're using it for and what stage you are at with it
(evaluation / testing / production)? Also, what alternatives you
evaluated/are evaluating would be useful.  Finally, feel free to throw
in "I'd love to use Cassandra if only it did X" wishes. :)

I can start: Rackspace is using Cassandra for stats collection
(testing, almost production) and as a backend for the Mail & Apps
division (early testing).  We evaluated HBase, Hypertable, dynomite,
and Voldemort as well.

Thanks,

-Jonathan

(If you're in stealth mode or don't want to say anything in public,
feel free to reply to me privately and I will keep it off the record.)