MQTT IoT topology

{
  "nodes": [
    { "id":"s1","type":"rounded","label":"Sensor 1","x":40,"y":40,"fill":"#dbeafe","stroke":"#2563eb" },
    { "id":"s2","type":"rounded","label":"Sensor 2","x":40,"y":160,"fill":"#dbeafe","stroke":"#2563eb" },
    { "id":"s3","type":"rounded","label":"Sensor 3","x":40,"y":280,"fill":"#dbeafe","stroke":"#2563eb" },
    { "id":"gw","type":"rect","label":"Edge gateway","x":260,"y":160,"fill":"#ede9fe","stroke":"#6d28d9" },
    { "id":"br","type":"rect","label":"MQTT broker","x":480,"y":160,"fill":"#fef3c7","stroke":"#a16207" },
    { "id":"d1","type":"rect","label":"Dashboard","x":700,"y":80,"fill":"#dcfce7","stroke":"#15803d" },
    { "id":"d2","type":"rect","label":"Alerting","x":700,"y":200,"fill":"#dcfce7","stroke":"#15803d" },
    { "id":"d3","type":"rect","label":"Time-series DB","x":700,"y":320,"fill":"#dcfce7","stroke":"#15803d" }
  ],
  "edges": [
    { "id":"e1","source":"s1","target":"gw" },
    { "id":"e2","source":"s2","target":"gw" },
    { "id":"e3","source":"s3","target":"gw" },
    { "id":"e4","source":"gw","target":"br","label":"publish" },
    { "id":"e5","source":"br","target":"d1","label":"sub /metrics" },
    { "id":"e6","source":"br","target":"d2","label":"sub /alerts" },
    { "id":"e7","source":"br","target":"d3","label":"sub /#" }
  ]
}