Websocket help on durable obejct

If i make a websocket as a service saas like pusher and host on cloudflare worker and durable objects

To sell to millions of users, do i need 1 worker? Or each user require separate worker?

I also want to know about storage limit as i am going to store on sql based storage on DO

Note: i don’t want cloudflare to make me buy enterprise plan in future as i don’t have that much money lol