Realtime Chat Architecture Diagram

{
 "schema_version": 1,
 "diagram_type": "architecture",
 "meta": {
  "title": "realtime chat system: websocket gateway fans out messages, p"
 },
 "components": [
  {
   "id": "n1",
   "type": "security",
   "label": "realtime chat system: websocket gateway ",
   "pos": [
    40,
    300
   ],
   "size": [
    340,
    60
   ]
  },
  {
   "id": "n2",
   "type": "database",
   "label": "presence cache in redis",
   "pos": [
    450,
    300
   ],
   "size": [
    215,
    60
   ]
  },
  {
   "id": "n3",
   "type": "database",
   "label": "message store in cassandra",
   "pos": [
    735,
    300
   ],
   "size": [
    238,
    60
   ]
  },
  {
   "id": "n4",
   "type": "backend",
   "label": "push notification service for offline us",
   "pos": [
    1043,
    300
   ],
   "size": [
    340,
    60
   ]
  }
 ],
 "connections": [
  {
   "from": "n1",
   "to": "n2"
  },
  {
   "from": "n2",
   "to": "n3"
  },
  {
   "from": "n3",
   "to": "n4"
  }
 ]
}