Hi, Alberto. Thanks for the questions.

With CacheServer max threads unset (the default), the number of ServerConnection threads is represented by the CacheServerStats currentClientConnections statistic. If max threads is set, then that setting will be the number of ServerConnection threads. ServerConnection threads process all client requests. On the client, those operations are implementations of the Op interface (e.g. PutOp, GetOp). On the server, those Ops are processed by implementations of the Command interface (e.g. Put70, Get70).

Extensions of DistributionMessage are sent between peers of the distributed system. One of those DistributionMessage extensions is PutMessage. A PutMessage is created when one peer receives a put request for a key that it is not primary for. In that case, a PutMessage is created and sent to the primary peer for that key, and a PartitionedRegion Message Processor thread in that primary peer processes that PutMessage.