Supposing that your server-side tech uses multiple workers to render pages, I suppose you have to serialize the access to the SQLite file. What is the best way to do this?
SQLite can handle concurrent reads, but needs to lock the entire DB when writing. Multiple workers shouldn't be a problem per se, but if you need multiple workers to support the traffic, then maybe a client-server db like postgres is a better choice.
Just about anything that's not facebook/twitter/google.
I think you underestimate how much load it can handle.