Yes, you can limit the number of connections per host in the Cassandra cluster.
If you are using the C++ driver, check this out.
I visualize any query following the below path:
Client --> Session --> IO threads --> Connections --> Nodes
You can configure the number of IO threads(This is the number of threads that will handle query requests) associated with the session. In each IO thread, you can then configure the number of connections per host. If needed, the number of connections per host will increase based on certain parameters(The maximum count up to which this can be increased is also configurable).
So, at max, there can be x number of connections per host where,
x = number_of_sessions * number_of_IO_threads * max_number_of_connections_per_host
All 3 variables on RHS in the above equation are configurable.
Also check out: