Advice on how to cut latency when calling onNext()

[Rio Zhu]

Hi All,

I'm having a bi-direction streaming service, the client is written in Java while the server is in C++. Both client and server side use the async gRPC APIs. Also, each channel, when created, sends a dummy message to the server, as a warmup.

I have noticed that, after warmup, when calling requestObserver.onNext() on the client side, the first few calls will take ~15 ms, and after that, it takes less time, which is <= 2ms. 

I'm wondering what is a good way to cut that inital latency so that it takes no more than 2 ms, just like the following calls?

Also, is it normal for onNext to take around 2ms to execute?

Thank you very much for your time and help.

Rio