I am currently using the CassFuture callback future to implement an asynchronous pattern for processing Cassandra queries. It appears that all of the callbacks are coming in on the same thread. Is this the expected behavoir?
Assuming you are using the current version of the driver (v2.9.0) the number of threads is configured via cass_cluster_set_num_threads_io() before creating a session and defaults to 1. If you increase the number of IO threads in the cluster configuration you will notice that CassFuture callbacks will begin to show up on different threads.
NOTE: If your callback is slow, consider running on a separate thread; otherwise the callback might block IO operations for other requests being executed on the callback/IO thread. Another recommendation is not use the complete number of cores/virtual cores available in your hardware configuration as this could starve resources from your client application (and potentially from the OS services).