Heroku: web dyno vs. worker dyno? How many/what ratio do I need?

Question

I was curious as to what the difference between web and worker dynos is on Heroku. They give a one sentence explanation on their pricing page, but this just left me confused

Answer 1

Short answer is that you need as many as you need to keep your queues down.

As John describes, if you start seeing a queue in your logs then you need more dynos. If you start seeing your background queues getting too long (how you get this info is dependant on what you have implemented) then you need more workers.

There is no ratio as it's very much dependent on your application design and usage.