[praptak]

> if you did switch from smart to naive routing, what was the rationale behind it?

Most probable cause: smart routing is hard to scale. Multiple routers, with each one doing random distribution independently of others will still produce a globally random distribution. No need for inter-router synchronization.

If multiple routers try smart routing, they must do quite a bit of state sharing to avoid situations where N routers try to schedule their tasks on a single dyno. And even if you split dynos between routers then you need to move requests between routers in order to balance them.