Heroku: Better to have one dedicated db for each app or one dedicated db for all apps?

Looking at Heroku's dedicated database plan.

Is it normal for several apps to run on one dedicated db (i.e. Ronin)? I've got 3 Rails apps. Was thinking of using a dedicated db (Ronin, thats running on PgSql).

Or is it wiser to have one app to a dedicated db? i.e. Each app ha开发者_StackOverflows their own dedicated db. What are your thoughts on this? What is the general convention?

Alternatively, was thinking of using Amazon RDS. Which would mean, having at least one RDS database instance for every app.

One dedicated db for all 3 apps:

You'll have more power on the front end apps and it's easier to maintain the db. But you could run into bandwidth connection issue on the db if you have a lot concurrent users.

One DB for each:

All the apps are standalone, hence db1 failure won't effect app 2, 3. but You pay the overhead of db three times.plus A lot admin work on dbs.

It really depends on the natural of the app, your budget(cluster db), user, etc.