Heroku's dynos scale just fine. As long as you got the money you can keep adding dynos. However Heroku's database services do not scale as easily. I recommen

Heroku's dynos scale just fine. As long as you got the money you can keep adding dynos. However Heroku's database services do not scale as easily. I recommend using Amazon's RDS instead. RDS is F'n amazing. You can scale the db up or down and take snapshots without any downtime.