The downloader currently queries the databse for apps that have not been downloaded.
It then attempts to download that app and if successful it then updates the database.

I do the downloading updates of the database in batches right now.

There is no way currently with the the downloader tool on the play store to ask for a specific version, this would require another query to check. Do not really want to bring in all the retreiver to the downloader.
If we setup up that we can pass a sort by oldest we could also also remove dates that are too old? reducing only the chance of the version mismatching. Unless we get unlucky and the second we scrape we have a update. @AdamSlack @sauyon thoughts?