Nope, it's much more simple than that. Each CSV upload is converted into a SQLite database. Then I deploy a static, read-only copy of that database to a Zeit Now hosting account and fire up my "datasette" command-line tool (written in Python 3) which opens the SQLite database and starts serving up queries from it.
The magic here is that the SQLite database is opened in read-only mode, which means I don't have to worry about concurrent access or write activity. SQLite is screamingly fast if you use it in this context.
Because the data is read-only, if you ever DO need to scale to handle more traffic you can do so by firing up additional instances, each with their own copy of the SQLite database file.
https://github.com/simonw/datasette
The magic here is that the SQLite database is opened in read-only mode, which means I don't have to worry about concurrent access or write activity. SQLite is screamingly fast if you use it in this context.
Because the data is read-only, if you ever DO need to scale to handle more traffic you can do so by firing up additional instances, each with their own copy of the SQLite database file.