That's actually exactly what i was trying to say. You set up your app so that you hit a limit of users (or whatever your main DB service is) and so you add ano

That's actually exactly what i was trying to say. You set up your app so that you hit a limit of users (or whatever your main DB service is) and so you add another cheap slave to the pool, as opposed to having one or two super important servers that need hardware upgrades to expand.