This is relevant for sparse datasets. If I have 100 columns in a table, most of which are NULL, with N rows. Would N or 100*N values be stored in the storage engine?
In YugaByte DB we don’t store NULL values, so it would be closer to N than 100*N.
Note: a subtlety arises in handling the rows where most columns (except, perhaps, primary key columns) are NULL. This is why we also store a special hidden system column that indicates row existence.
Please refer to https://docs.yugabyte.com/latest/architecture/docdb/persistence/ for more information about how YugaByte DB maps the relational data model onto the underlying key-value store.