Similar to Riak post-commit hooks:
Like traditional database triggers, Cassandra Async trigger is a procedure that is automatically executed by the database in response to certain events on a particular database object (e.g. table or view). The distinguishing feature of Async trigger is that the database responds to the client on successful update execution without waiting for triggers to be executed, thus reducing response latency.
In case you wonder how to use them this might give you an idea.
Cassandra has (Async) Triggers originally posted on the NoSQL blog: myNoSQL