If you used HiveMQ Cloud Serverless because you wanted an MQTT broker without running servers, the closest replacement is another serverless MQTT broker: a private broker on a shared, tenant-isolated cluster that you create in a web console and connect to with standard clients. The ConnectMQ Cloud Serverless MQTT Broker is built for exactly that. This article shows what it offers, how its plans map to HiveMQ Serverless Free and Pay As You Go users, and how to move your first client.
HiveMQ retires Serverless on December 31, 2026; see HiveMQ Cloud Serverless end of life for the details.
What You Should Expect From a Serverless Replacement
A good HiveMQ Serverless alternative keeps the things that made Serverless attractive:
- No infrastructure. No virtual machines, certificates or patches to manage.
- A free tier that is useful for real devices and real TLS, without a credit card.
- Standard MQTT so your existing client code keeps working.
- A web console to create credentials and see what your devices are doing.
- A path upward to more connections or an isolated cluster without changing protocols.
ConnectMQ Serverless at a Glance
| Feature | Serverless (Free) | Serverless (Paid) |
|---|---|---|
| Concurrent connections | Up to 25 | Up to 1,000 |
| Maximum QoS | 1 | 2 |
| Maximum message size | 256 KB | 1 MB |
| Retained messages and wildcards | Yes | Yes |
| Shared subscriptions | No | Yes |
| MQTT versions | 3.1.1 and 5.0 | 3.1.1 and 5.0 |
| Credit card required | No | Yes |
Both plans run on a shared, multi-tenant cluster where each broker is isolated: your credentials, your topic space and your quotas. A subscription to # only ever returns your own traffic. When you need more than 1,000 connections or an isolated cluster, the Managed Cloud MQTT Broker is the next step, using the same protocol and tooling. The serverless MQTT broker guide explains the model in depth.
Mapping From HiveMQ Serverless
| If you were on | Typical situation | Suggested ConnectMQ plan |
|---|---|---|
| HiveMQ Serverless Free, prototype or hobby project | A few devices, a dashboard, testing | Serverless (Free) |
| HiveMQ Serverless Free, growing pilot | Approaching 25 devices, needs QoS 2 or larger payloads | Serverless (Paid) |
| HiveMQ Serverless Pay As You Go, production | Hundreds of devices, backend services | Serverless (Paid), or Dedicated for isolation |
| Many backend consumers on the same stream | Load balancing across workers | Serverless (Paid) with shared subscriptions |
Check the current limits of your HiveMQ cluster in its console and size the new plan to your peak connection count plus headroom, not to the average.
Endpoints and Security
| Transport | Port | Notes |
|---|---|---|
| MQTT | 1883 | For testing on trusted networks |
| MQTT over TLS | 8883 | Recommended for devices |
| WebSocket | 8083 | For browser testing |
| Secure WebSocket | 8084 | Path /mqtt, for web dashboards |
TLS uses a publicly trusted Let's Encrypt certificate, so standard clients trust it without custom CA files. Each broker gets a generated username, password and client ID. The client ID is bound to the credentials, and clients may append a suffix, such as YOUR_CLIENT_ID_kitchen, to run several connections under one credential set. Shared infrastructure is protected with per-plan quotas, connection-flood protection and IP blocking after repeated failed logins, and MQTT 5 clients receive clear reason codes, such as 0x97 for quota exceeded.
Built-In Tools You Do Not Have to Install
The ConnectMQ portal includes:
- An in-browser MQTT client to publish and subscribe without any software.
- A live topic explorer that shows topics and payloads as they arrive.
- A dashboard with connection and traffic overviews.
- A devices view organised by ISA-95 levels, with Sparkplug B decoding for industrial payloads.
- Threshold alert rules and an alerts log.
During a migration these tools are the quickest way to confirm that each wave of devices arrives with the expected topics and payloads.
Connect Your First Migrated Client
Create a free broker at app.connectmq.com, copy the credentials and change only the connection settings in your client. With MQTT.js:
// npm install mqtt
const mqtt = require("mqtt");
const client = mqtt.connect("mqtts://broker.connectmq.com:8883", {
username: process.env.MQTT_USERNAME,
password: process.env.MQTT_PASSWORD,
clientId: `${process.env.MQTT_CLIENT_ID}_dashboard`,
protocolVersion: 5,
});
client.on("connect", () => {
console.log("Connected to ConnectMQ");
client.subscribe("site1/#", { qos: 1 });
});
client.on("message", (topic, payload) => {
console.log(topic, payload.toString());
});
Your topics, payloads and QoS stay the same as on HiveMQ. Only the host, port, credentials and client ID change. Examples for ESP32, Python and Node-RED are in Reconfigure MQTT clients after HiveMQ.
What Is Different From HiveMQ Cloud
A fair comparison includes the differences you should plan for:
- Client IDs are bound to the issued credentials rather than freely chosen.
- Per-topic permissions are not offered; separate trust boundaries with separate brokers or credentials.
- Retained state should be republished by clients on connect rather than relied on across broker restarts.
- Data integrations are done with standard MQTT clients such as Node-RED, Telegraf or your own subscribers, rather than built-in connectors.
For most Serverless workloads these are small configuration changes. If one of them is a blocker for you, the full migration guide shows how to work around it.
Frequently Asked Questions
Is ConnectMQ Serverless free?
Yes. The Serverless (Free) plan supports up to 25 concurrent connections, QoS up to 1 and 256 KB messages, with retained messages and wildcard subscriptions, and needs no credit card.
Can I start free and upgrade later without changing devices?
Usually yes. Upgrading changes quotas while your protocols, ports and topic structure stay the same; at most you update the credentials or endpoint shown in the portal. Moving to a Dedicated cluster typically means a new hostname and credentials, while the MQTT logic stays unchanged.
Does ConnectMQ support MQTT 5 like HiveMQ Cloud?
Yes. Both MQTT 3.1.1 and MQTT 5.0 are supported, including reason codes, user properties and session expiry. Shared subscriptions are available on Serverless (Paid) and above.
How quickly can I replace my HiveMQ Serverless cluster?
Creating the broker takes a few minutes. The total time depends on how quickly you can update your clients; for applications and dashboards it is often the same day.
