How do you aggregate the data and query among all those databases? Doesn't it incur huge costs? Does sqlite support this natively or are you basically treating it as text files of data per user and don't need complex queries in the first place?
We don't have any use cases for querying across these datastores right now. Hypothetically, if we did need something like this it would probably be an offline ETL analysis tool. I have written a few of these and they can be incredibly performant if everything lives on the same box.