EMQX

Erlang MQTT broker for large IoT fleets, relicensed to BSL with production free use limited to one node

As of 31 August 2026, EMQX has a free plan and paid plans start at $234/month. A distributed MQTT broker written in Erlang that handles very large numbers of concurrent device connections and includes a rule engine for routing messages into databases. Softwr lists it under Databases. EMQX is made by EMQ Technologies, available on Linux, Docker, Kubernetes, Cloud.

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Overview

What EMQX does

EMQX is an MQTT message broker built on Erlang/OTP, designed for IoT deployments with millions of concurrent device connections. It implements MQTT 3.1.1 and 5.0 with clustering, shared subscriptions and session persistence, and adds a rule engine and data integration layer that routes messages directly into Kafka, PostgreSQL, InfluxDB, MongoDB, S3 and dozens of other sinks without an intermediate consumer application. It also speaks MQTT over QUIC, CoAP, LwM2M and MQTT-SN for constrained devices. The fact that should change a shortlist is the licence. With version 5.9, released in May 2025, EMQ merged the community and enterprise editions into one product and moved it from Apache 2.0 to Business Source Licence 1.1. Every feature that was previously enterprise-only is now visible in the source, but the additional use grant permits free production use of a single node only. Clustering, which is the entire reason to choose EMQX over Mosquitto, now requires a commercial subscription. Each version reverts to Apache 2.0 four years after release. Buyers are IoT platform teams, connected vehicle programmes and industrial operators with device counts that break single-node brokers. The trade-off is that the previous free path to a production cluster is closed, so the calculation against HiveMQ, NanoMQ or self-operated Mosquitto now has to include a real licence cost from day one of the second node.

What people use it for

A connected vehicle platform needing millions of persistent MQTT sessions with QUIC for handover across mobile networks
An industrial operator routing sensor telemetry straight into TimescaleDB or Kafka without writing a consumer service
An IoT product team that has outgrown a single Mosquitto instance and needs clustering and shared subscriptions
A smart building deployment mixing MQTT, CoAP and LwM2M devices on one broker

Where it falls short

Concrete and checkable, so you can decide whether any of them matter to you. This is the half of a review a vendor will not write about EMQX.

The move to Business Source Licence 1.1 at version 5.9 in May 2025 limits free production use to a single node, so the clustering that justifies choosing EMQX now requires a paid subscription from the second node onward.
The relicensing arrived in a minor release, which caught users who had pinned to 5.x expecting Apache 2.0 terms and forced legal review of existing deployments.
Running an Erlang/OTP cluster well requires operational knowledge most teams do not have, and diagnosing distribution, mnesia or memory issues means learning a runtime you use for nothing else.
Enterprise pricing is quoted rather than published for the self-managed edition, so the cost of the clustered configuration you actually need is invisible until you talk to sales.
The Serverless tier caps at around a thousand connections and shares infrastructure, which makes it a prototyping tier rather than a genuine small production option.

Cross-shopped

What people choose instead of EMQX

Each pairing was judged by two reviewers asking whether a buyer would genuinely weigh the two against each other. The ones that failed were deleted rather than published.

EMQXvs
NATS
NATS: If you want a genuinely Apache 2.0 messaging system with clustering and can use its own protocol rather than MQTT
EMQXvs
RabbitMQ
RabbitMQ: If you need broad protocol support including MQTT under an unchanged open source licence
EMQXvs
Ably
Ably: If you would rather buy a fully managed realtime messaging service than operate a broker at all

Pricing

What EMQX costs

Taken from the vendor's own pricing page. Prices move, so check before you buy.

Open Source single node

Free

BSL 1.1 licence since version 5.9
Free production use of one node only
All former enterprise features visible
Reverts to Apache 2.0 four years after each release

Serverless

Free

Free monthly quota then pay as you go
Up to 1,000 connections
8 by 5 support
Shared multi-tenant infrastructure

Dedicated Flex

$234 /mo

Single tenant cluster
Traffic allowance included
24/7 support
1 MB maximum message size

Enterprise self-managed

On request

Deploy on premises, at the edge or in any cloud
Clustering licensed
256 MB maximum message size
Professional services and custom plugins

Capabilities

Features

Erlang clustering
Horizontal scale-out across nodes with shared subscription distribution
MQTT 5.0 and QUIC
Full MQTT 5 feature set plus MQTT over QUIC for lossy mobile networks
Rule engine
SQL-like rules that filter and transform messages inside the broker
Data integration sinks
Direct bridging to Kafka, PostgreSQL, InfluxDB, MongoDB, Redis, S3 and more
Session persistence
Durable sessions surviving broker restart and node failure
Multi protocol gateways
CoAP, LwM2M, MQTT-SN and Stomp alongside MQTT
Authentication and authorisation
Database, JWT, LDAP and mTLS backed access control per topic
Dashboard and REST API
Cluster management, client inspection and metrics over HTTP

Answered, with sources

Questions people ask

Each answer names the page it came from, so you can check it rather than take our word for it.

Is EMQX still open source?

Not in the OSI sense since version 5.9. It is source-available under Business Source Licence 1.1, reverting to Apache 2.0 four years after each release.

Can I run a free cluster?

No. The additional use grant permits free production use of one node; clustering requires a commercial licence.

What changed for existing users?

Community and enterprise editions merged, so all features are now visible, but the licence terms tightened in the same minor release.

Which version is still Apache 2.0?

Releases before 5.9 remain under Apache 2.0, and each BSL release converts to Apache 2.0 four years after publication.

Keep looking

Where to go from EMQX

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Softwr does not host reviews and shows no star rating for EMQX, because a rating we did not collect is not ours to publish. What is here is the pricing and platform detail from the vendor’s own pages, limitations we could state concretely, and alternatives a reviewer confirmed people weigh against it. Tell us if any of it is wrong.

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