I tried profiling a gRPC java server. And i see the below set of thread pools majorly.
As far as I know you can specify using the directExecutor() when building the GRPC server / client that will ensure all work is done in the IO thread and so threads will be shared. The default is to not do this for safety reasons as you will need to be very careful about what you do if you are in the IO Thread (like you should never block there).