Since everything depends on the specific workload. It is sort of dynamic so you will have to test your specific load to find out the limit.
It will depend on:
- On the size and the rate of messages you will be sending.
- The number of clients (both subscribers and publishers).
- The characteristics of performance you need to meet.
- And also many more other factors.
So there is no way to tell the exact number and you will have to perform your tests to find out the limits.