Timestamps are not used by counters and TTL are not supported, but it appears we don't reject counter updates that have "USING TIMESTAMP X" or "USING TTL X". We should since both are non-sensical (the value is completely ignored currently).
Note: we should also refuse "USING TIMESTAMP" on "DELETE" statements on counters table: even though we kind of do use a timestamp internally, it's more of an implementation detail and in fact may go away with CASSANDRA-6506 (there is also nothing clever you can do with it by providing it client side).
Note bis: strictly speaking doing that could break a few users that where setting those thinking it does something. I think that the lack of validation is more of a bug and that user that think it's doing something probably ought to know it's not sooner than later, but I could be fine with just warning in the log file for 1.2 and 2.0, and only rejecting in 2.1 if someone thinks it's safer.
- is related to