We are storing our record keys with the sendKey property of the write policy set. This is very useful for scans when there is no other way to get that data. I was wondering where is the plaintext value of the key stored - is it just stored on disk or does it increase the in-memory key size requirement?
The key information is stored with the record, so it does take some of the record space. You should take that into account with relation to the max record size, which is the write-block-size.