The algorithm behind the delete

Good day, the question is rather theoretical. I don’t use budget in production but I am willing to give it a try. One think I don’t understand is how do you handle deletes/updates. General LSM trees mark the value in sstable as thomb, during the lookup if thomb value has the biggest timestamp it means key was deleted. But in badger case you don’t store the value in lsm . So do you store some boolean flag along with a key inside of sstable and mark this boolean as deleted ? How this deletion algorithm works ? Thanks in advance