title: Opnsource MQTT Broker(websocket support) for large number of active users with fewer messages to each user
body: <p>I have been looking for last 4 days on anything/everything related to MQTT OpenSource broker. Me, being fairly new to MQTT. It would be great if someone can help.</p>
  
  <p>I am working on an App in which I need push notifications support. 
  The app will be used as native mobile apps and webApps(running in browsers). After having some initial research I don't want to use GCM/FCM. I plan to use open-source MQTT broker with socket.io. An ideal use-case of push-notification will be as following:</p>
  
  <p>There will be 1 million active users. </p>
  
  <p>There will be 50-100 groups and each user will be subscribed to about one or two groups mostly with 5-10(max) msgs received from the subscriber per day. </p>
  
  <p>In near-future there must be a possibility of adding chat support between users. Though the chat functionality will be used occasionally between users with few msgs, availability is of prime concern QoS level 1/2.</p>
  
  <p>In future if the users increase we will need to scale.
  I plan to use mosquitto-broker. My main concern is Will this be suited for this use-case ? How much ram will I need to have in server, if I don't use SSL.</p>
  
  <p>If not, can it be achieved using to Mosca preferred(reason node-js) or emqttd.</p>
  
  <p>My backend consists of express-js server and mongo-db running on Ubuntu. </p>
  
  <p>Thanks</p>