I have developed chat application like whatsapp using openfire server version 4.0.2.
We have successfully rolled out our application and currently we have around 55k users in android and iphone application.
we haven’t use clustering for load balancing. so some time server becomes very slow to respond to new connection as well as existing connection and new user can not make connection.
Right now we are using java heap memory 6GB for server and 4 core processor I can share additional information if needs.
Right now we do have only 1k concurrent user still we are facing and our expecation is to handle more then 1 million user and 10k concurrent session so anybody who can suggest best configuration then please respond.
We are willing to pay for it.