EMQX

What is EMQX?

EMQX is an open source, distributed MQTT broker for IoT. Written in Erlang, it clusters across multiple nodes to connect huge numbers of devices — the project claims 100M+ concurrent MQTT clients across a cluster — and routes their pub/sub messages in real time, with a built-in SQL rule engine for processing and forwarding that data.

What is EMQX best for?

Large or fast-growing IoT deployments — connected vehicles, industrial sensors, smart cities — where a single-node broker isn’t enough and you need horizontal scaling, high availability, and built-in data integration to databases and streaming platforms, all on infrastructure you control.

What can EMQX do?

• Speak MQTT 5.0, 3.1.1, and 3.1, plus MQTT over QUIC, MQTT-SN, CoAP, and LwM2M
• Cluster across nodes for high availability and scale to 100M+ concurrent connections
• Process and route messages with a SQL-based rule engine, no external stream processor needed
• Bridge data to 50+ systems — Kafka, PostgreSQL, MongoDB, Redis, and more — via built-in connectors
• Build data pipelines visually with the Flow Designer, and validate payloads with a Schema Registry
• Secure connections with TLS/SSL, multiple authentication backends, and per-topic ACLs

Where does EMQX fall short?

• Its license restricts clustered production use. As of v5.9, EMQX is under the Business Source License 1.1 — source-available, not OSI open source. The free grant covers non-production use and single-node production; running a production cluster commercially requires a paid license (each version converts to Apache 2.0 four years after release).
• It’s overkill for small fleets. If you’re connecting a few hundred or few thousand devices, a lightweight broker like Eclipse Mosquitto is simpler to run and lighter on resources than an Erlang cluster.
• It’s an MQTT broker, not a general message queue. For app-to-app task queues or high-throughput event streaming between backend services, purpose-built tools like RabbitMQ or Apache Kafka are a better fit than a device-facing MQTT broker.

Is EMQX free?

Yes to self-host in most cases — EMQX is free to run for non-production use and for single-node production deployments under its BSL 1.1 grant. Running a production cluster for commercial use requires a paid Enterprise license. EMQX also offers a managed cloud: a Serverless tier that starts free (up to 1,000 connections, pay-as-you-go beyond), Dedicated clusters from around $234/month, and BYOC/Enterprise plans with custom pricing.

What does EMQX replace?

EMQX is a self-hosted alternative to managed IoT messaging services like AWS IoT Core and Azure IoT Hub, and to the commercial HiveMQ enterprise broker. It does the same device-connectivity and pub/sub job, but you run it on your own infrastructure without per-connection or per-message cloud billing.

FAQ

Is EMQX open source? Partly. Through v5.8 EMQX was Apache 2.0; from v5.9 it moved to the Business Source License 1.1, which is source-available rather than OSI open source. The code is public and each release converts to Apache 2.0 four years after it ships.

Can I self-host EMQX for free? Yes for non-production use and for single-node production deployments. A commercial production cluster needs a paid Enterprise license, so the free path suits development, testing, and smaller single-node setups.

Is EMQX a good HiveMQ or AWS IoT Core alternative? For large self-hosted fleets, yes — it clusters to very high connection counts and includes a rule engine and data integrations out of the box. If you want a fully managed service with no servers to run, AWS IoT Core or EMQX’s own cloud may be easier.

What do I need to run EMQX? A Linux server (Docker or a package install) for a single node; for production clustering you’ll run multiple nodes, typically on Kubernetes via the EMQX Operator, plus a commercial license.