> But if you're absolutely sure you need to be planning to run at close to Twitter or Facebook scale one day, then yep, you'd better architect from the beginnin

> But if you're absolutely sure you need to be planning to run at close to Twitter or Facebook scale one day, then yep, you'd better architect from the beginning not to use joins. No, both of them started with MySQL. If you make it, you have plenty of resources to throw at the scaling problem, it's a good problem to have. A bad problem to have is running out of money and shutting down because you over engineered from the start. Don't do that. Most startups fail, and you're no exception. Build one to throw away, and if you're lucky enough to succeed, you can use your new-found resources to rebuild what needs to be rebuilt.