This is about the architecture of my application I think. I have a Rails application where companies can administrate all things related to clients. Companies can buy a subscription and their users can access the application online. Hopefully I will get multiple companies subscribing to my appplication/service. Thing is, what should I do with my code and database?

• Seperate app code base and database per company
• One app code base but seperate database per company
• One app code base and one database

The decision I am to make involves security (e.g. user from company X should not see any data from company Y) performance (let's suppose it becomes successful, it should have a good performance) and scalability (again, if successful, it should have a good performance but also easy for me to handle all the companies, code changes, etc)

For sake of maintainability, I tend to opt for the one code base. For the database I really don't know at this moment. So what do you think is the best option?