MQTT and SCADA integrations for web developers

Web developers can build IoT systems

When I joined Renewalytics, I was a web developer. I'd never heard of MQTT, OPC-UA, or SCADA. Two years later, I've built a production telemetry system ingesting data from dozens of renewable energy plants. The learning curve is steep but manageable if you come from a web background.

What is SCADA?

SCADA (Supervisory Control and Data Acquisition) is the backbone of industrial systems. Every solar plant, wind farm, and factory has SCADA systems monitoring equipment in real time, power output, temperature, voltage, alarm states.

The challenge: SCADA systems speak industrial protocols (Modbus, OPC-UA), not HTTP. To build a modern web dashboard on top of SCADA data, you need a translation layer.

MQTT: the bridge

MQTT is a lightweight publish-subscribe messaging protocol. Think of it as WebSockets for IoT. A device publishes telemetry to a topic, and any subscriber gets it instantly.

Solar Plant → SCADA → MQTT Broker → Your App

In practice, most modern SCADA gateways can publish to MQTT natively or through a middleware.

Building the ingestion service

import mqtt from "mqtt";
 
const client = mqtt.connect(process.env.MQTT_BROKER_URL, {
  username: process.env.MQTT_USERNAME,
  password: process.env.MQTT_PASSWORD,
});
 
client.on("connect", () => {
  // Subscribe to all plant telemetry topics
  client.subscribe("plants/+/telemetry/#");
  console.log("Connected to MQTT broker");
});
 
client.on("message", async (topic, message) => {
  // topic: plants/PLANT_001/telemetry/generation_kw
  const [, plantId, , metricName] = topic.split("/");
  const value = parseFloat(message.toString());
 
  await db.telemetry.create({
    data: {
      plantId,
      metric: metricName,
      value,
      timestamp: new Date(),
    },
  });
});

OPC-UA for direct SCADA access

When MQTT isn't available, OPC-UA gives you direct access to SCADA data points. It's more complex but more powerful:

import { OPCUAClient, DataType } from "node-opcua";
 
const client = OPCUAClient.create({ endpoint_must_exist: false });
await client.connect(process.env.OPCUA_ENDPOINT);
 
const session = await client.createSession();
 
// Read a specific data point
const result = await session.read({
  nodeId: "ns=2;s=Plant.Generation.ActivePower",
  attributeId: 13, // Value attribute
});
 
console.log(result.value.value); // e.g., 1523.7 (kW)

Lessons from production

1. Buffer writes, don't write every MQTT message to the database individually. Batch them in 5-second windows.
2. Handle stale data, if a plant stops sending data, your dashboard should show "last updated 10 min ago", not stale values that look current.
3. Alarm deduplication, SCADA systems can send the same alarm hundreds of times. Deduplicate by alarm code + plant + time window.
4. Time zone hell, plants are in different time zones. Store everything in UTC. Convert for display only.

The web developer advantage

Coming from web development, I brought modern tooling to a domain still running on legacy desktop apps. A Next.js dashboard with WebSocket updates is objectively better than the 20-year-old SCADA HMI software most plants use.

If you're a web developer interested in IoT, industrial automation, or climate tech, the demand is huge and the competition is thin. Start with MQTT. Build a dashboard. The skills transfer directly.