Cassandra easy
When you DELETE a record in Cassandra, it is not immediately removed from disk. What is the name of the 'delete marker' that is written to note the deletion?
- A A 'Ghost Fragment' that remains invisible to the database engine.
- B A 'Tombstone', a special record with a timestamp that indicates the data has been logically deleted.
- C A 'Zombie Hook' that allows the data to be resurrected if needed.
- D A 'Placeholder Zero' that fills the disk space with empty bits.
Answer: B. A 'Tombstone', a special record with a timestamp that indicates the data has been logically deleted.
Cassandra's data files (SSTables) are immutable (cannot be changed). To 'Delete' something, Cassandra writes a 'Tombstone' mark. Eventually, during a background 'Compaction' process, the old data and the Tombstone are merged and permanently discarded from the disk.
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