There are some interesting points here on how Heroku internals can affect your app:
> An important outcome of these tests is that the slow-response situation is outside of your control unless you’re running single-tenant (performance) dynos.
> An important outcome of these tests is that the slow-response situation is outside of your control unless you’re running single-tenant (performance) dynos.
If you are on shared tenancy dynos, and your current configuration is nearing maximum capacity, then adding dynos can reduce performance. Not per dyno, but across the entire platform.
Counter-intuitive but true.