You don't - it's one server only, with the database WAL (transaction log) being shipped to S3 for backup/restore.
You can run multiple Django processes to scale up on a single server, and of course get a server with more cores. The one limitation is that you can't have more than one process writing to an SQLite database at the same time... but you can have a *lot* of readers.
And as the database is local, the latency is super low.