Cassandra Tombstones ?

Cassandra tombstones ? 

During a dev I get this strange message about query generating warning for Tombstones..

Image result for tombstone cassandra
Some explanations here:

Deleting distributed and replicated data from a system such as Apache Cassandra is far trickier than in a relational database. The process of deletion becomes more interesting when we consider that Cassandra stores its data in immutable files on disk. In such a system, to record the fact that a delete happened, a special value called a “tombstone” needs to be written as an indicator that previous values are to be considered deleted. Though this may seem quite unusual and/or counter-intuitive (particularly when you realize that a delete actually takes up space on disk), we’ll use this blog post to explain what is actually happening along side examples that you can follow on your own.
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