Hi,
It seems the library does not removed the nodes, which is already added to the db, during the updating. The old nodes are only removed in the live cache, rather than in the db. So if one node is commit to the db, it will stay there forever. For example, if I run the code:

keys := getFreshData(10000, 32)
for i := 0; i < 30; i++ {
    values := getFreshData(10000, 32)
    smt.Update(keys, values)
    smt.Commit()
}

The size of the db keeps growing, even the keys do not change.