DB setup for Web2 online applications

I'm planning to code a Web2 online application and I'm looking for best-practices.

I'm talking about online apps similar to web collaborative or billing apps. I'm wondering how they setup their DB? Do they put all the users info in the same DB, or does eac开发者_StackOverflowh user have their own DB?

Take a look at Multi-Tenant Data Architecture.

Generally, everyone is going to be in the same DB. Different users or accounts are differentiated by a unique identifier (obviously). Once they need to scale beyond a single database, they will set up replication or clustering to distribute the load across different DB servers. These servers are mirrors of each other data.