6.8 mill tokens, delete old tokens? (cassandra storage)

Hi,

I recently upgraded our cluster from 2.0.5 to 2.1.4 and in that upgrade it did a migration on oauth2 tokens which took our cassandra cluster of 3 nodes almost 2h to do a migration on.

How can I easily clean up old tokens in production without killing everything ?
would it just to run a CQL query that looks at created_at - expires_in or is there a clever way to do this?

And why doesn’t Kong automatically cleanup old tokens that are expired?