Which web server and database?

Check if some process on system causes excessive load and that Load avarages never go above the cpu core count on server.
Make sure the server has enough memory and wont run out of it when forum is running.

You can also try adjusting Traffic management from "Settings --> advanced" to prevent "false" 503 page triggering.

When i try to access /groups/administrators (group is set visible), i get following error:

/groups/administrators Not Found
You seem to have stumbled upon a page that does not exist. Return to the home page.

Here's query from database: http://paste.kde.org/pyoyy68xj/1hvqu0

Any ideas how to fix this?

Have you got it to work yet?

I tried giving dbOwner permission to nodebb user but still get that error.

db.getUser("nodebb")
{
        "_id" : "nodebb.nodebb",
        "user" : "nodebb",
        "db" : "nodebb",
        "roles" : [
                {
                        "role" : "dbOwner",
                        "db" : "nodebb"
                }
        ]
}

That seems to do the trick.
Thanks

So i'm trying to use redis as websocket store because of clustering but after i add redis section to config.json and start nodebb i get error.

Starting NodeBB
  "./nodebb stop" to stop the NodeBB server
  "./nodebb log" to view server output
  "./nodebb restart" to restart NodeBB

 /path/to/nodebb/node_modules/nconf/lib/nconf/stores/file.js:141
      throw new Error("Error parsing your configuration file: [" + self.file +
            ^
Error: Error parsing your configuration file: [/path/to/nodebb/config.json]: Unexpected string
    at File.loadSync (/path/to/nodebb/node_modules/nconf/lib/nconf/stores/file.js:141:13)
    at Provider.add (/path/to/nodebb/node_modules/nconf/lib/nconf/provider.js:137:23)
    at Provider.file (/path/to/nodebb/node_modules/nconf/lib/nconf/provider.js:63:15)
    at Object.<anonymous> (/path/to/nodebb/loader.js:14:20)
    at Module._compile (module.js:460:26)
    at Object.Module._extensions..js (module.js:478:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Function.Module.runMain (module.js:501:10)
    at startup (node.js:129:16)

My config.json with redis added

 {
    "url": "http://nodebbsite.tld",
    "port": ["4567", "4568", "4569", "4570"],
    "secret": "***",
    "database": "mongo",
    "mongo": {
        "host": "127.0.0.1",
        "port": "27017",
        "username": "***",
        "password": "***",
        "database": "***"
    }
    "redis": {
       "host":"127.0.0.1",
       "port":"6379",
       "username":"",
       "password":"",
       "database":"0"
    }
}

Any ideas how to fix this?