Currently, the driver does not handle concurrent requests for the same class in an optimized way. The only synchronization that occurs is at the cache level. Consequently, since requests are never really simulateneous, multiple requests for the class will be sent to the same client, before a corresponding cache entry is created.

When a class loading request comes from a node, it is added to a queue in the client channel, which then processes them sequentially. Currently, once a request is in the client channel queue, it is too late to take advantage of the cache, even if a cache entry was created while the request was waiting in the queue. So this is very inefficient.

What we propose is that, when the disconnection of the client is detected, instead of just sending a null response for each pending class loading request, we make a "last chance" lookup in the cache, in the hope that the corresponding entry exists at that time. Actually, We could add a cache lookup for pending requests each time an operation is performed on the request queue, this should provide a nice improvement without changing much code.