How are you getting the concurrent user metric? Typical stats from php are aggregate counts over a period of time, and are not truly concurrent.
NodeBB can handle 500+ concurrent connections easily, but a cluster setup is advised to do so.
I need get some data from redis database to show in the other GUI. Would you tell me how to get the data defining of redis database please.
It is in the root folder of your installation in a file called config.json.