Well, the database cache is not managed by the plugin, so I don’t know how it is stored. It is stored somewhere on the server, but I honestly don’t know where to look for it.
But, if you have not generated the index table, then it should not be the issue. The regular engine does not store any additional information, it uses the original database table.
Can you try downloading the wp-contents/uploads/asp_upload folder, and check it’s size? It should contain all the files generated by the plugin. There are a few CSS files, some temporary files and cache when it is enabled. But it should not contain 5G of data for sure, may a few MB or so.
Can you please check that?
I want to make sure there is no issue there.