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Databases · head to head

CouchDB vs EMQX

CouchDB logo

CouchDB

Databases

Seamless multi-master sync with Apache CouchDB

From
Free
Rated
-
Full reviewWebsite
EMQX logo

EMQX

Databases

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

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: CouchDB append-only storage model may have performance implications for certain workloads with high update rates; 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.
  • They diverge on capability: CouchDB covers Multi-master Replication, EMQX covers Erlang clustering.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which CouchDB and EMQX actually diverge.

Attributes where CouchDB and EMQX differ
AttributeCouchDBEMQX
Pricing modelopen-sourcePer month by connection and session volume
PlatformsDocker, Windows (x64), macOS, Linux (Debian, Ubuntu, RHEL, CentOS), Raspberry PiLinux, Docker, Kubernetes, Cloud, macOS
Founded1999Unknown

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Databases).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in CouchDB

  • Multi-master Replication
  • HTTP/JSON API
  • MapReduce Views
  • ACID Semantics
  • Offline-first
  • Conflict Resolution
  • Fauxton UI
  • PouchDB

Only in EMQX

  • Erlang clustering
  • MQTT 5.0 and QUIC
  • Rule engine
  • Data integration sinks
  • Session persistence
  • Multi protocol gateways
  • Authentication and authorisation
  • Dashboard and REST API

What people use each for

The jobs each tool is most often brought in to do.

CouchDB

  • Offline-first applications requiring seamless replication across mobile and server environmentsnot EMQX
  • Multi-master deployments where data consistency eventually resolves across regionsnot EMQX
  • IoT and edge computing scenarios with intermittent connectivitynot EMQX

EMQX

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

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

CouchDB

  • Append-only storage model may have performance implications for certain workloads with high update rates
  • Requires network synchronisation for cluster data consistency; can introduce latency in multi-master scenarios
  • No explicit support for complex joins; MapReduce queries may be inefficient compared to relational databases

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.

Pricing, plan by plan

CouchDB

Free

No published plan breakdown. See the CouchDB review.

EMQX

Free
  • Open Source single nodeFree
    • BSL 1.1 licence since version 5.9
    • Free production use of one node only
    • All former enterprise features visible
  • ServerlessFree
    • Free monthly quota then pay as you go
    • Up to 1,000 connections
    • 8 by 5 support
  • Dedicated Flex$234/month
    • Single tenant cluster
    • Traffic allowance included
    • 24/7 support
  • Enterprise self-managed$undefined/year
    • Deploy on premises, at the edge or in any cloud
    • Clustering licensed
    • 256 MB maximum message size

Which should you pick?

Choose CouchDB if

  • You need multi-master replication.
  • You want to start without paying.
  • You work on Docker, Windows (x64), macOS, Linux (Debian, Ubuntu, RHEL, CentOS), Raspberry Pi.
  • You also want http/json api.
CouchDB review

Choose EMQX if

  • You need erlang clustering.
  • You want to start without paying.
  • You work on Linux, Docker, Kubernetes, Cloud, macOS.
  • You also want mqtt 5.0 and quic.
EMQX review

Questions people ask

Is CouchDB or EMQX better?
Neither clearly leads. CouchDB starts at Free and EMQX at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, CouchDB or EMQX?
CouchDB starts at Free and EMQX at Free.
Does CouchDB or EMQX run on more platforms?
CouchDB runs on Docker, Windows (x64), macOS, Linux (Debian, Ubuntu, RHEL, CentOS), Raspberry Pi. EMQX runs on Linux, Docker, Kubernetes, Cloud, macOS.
Can I use CouchDB for free?
Both have a free tier, so you can try either at no cost before committing.
What is CouchDB best used for?
CouchDB is most often used for offline-first applications requiring seamless replication across mobile and server environments, multi-master deployments where data consistency eventually resolves across regions, iot and edge computing scenarios with intermittent connectivity. Of those, offline-first applications requiring seamless replication across mobile and server environments and multi-master deployments where data consistency eventually resolves across regions are not what EMQX is typically brought in for.
What can CouchDB do that EMQX cannot?
CouchDB covers Multi-master Replication, HTTP/JSON API, MapReduce Views, ACID Semantics. EMQX covers Erlang clustering, MQTT 5.0 and QUIC, Rule engine, Data integration sinks.

Answered from the vendors’ own pages

CouchDB: Is Apache CouchDB free to use?

Yes, Apache CouchDB is completely free to download and use. It is open source software licensed under the Apache License 2.0.

Source
EMQX: 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.

CouchDB: Can I use CouchDB for commercial purposes?

Yes, the Apache License 2.0 permits commercial use. The license is permissive and does not restrict business applications.

Source
EMQX: Can I run a free cluster?

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

CouchDB: Is there a paid support or professional services option?

CouchDB's homepage mentions Professional Services as an available option, but no pricing details or specific service costs are listed. Contact the Apache CouchDB project for more information.

Source
EMQX: 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.

CouchDB: Who handles hosting costs if I use CouchDB?

CouchDB is self-hosted, so you are responsible for your own infrastructure and hosting costs. The software itself is free.

Source
EMQX: 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.

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