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Databases · head to head

Azure SQL vs EMQX

Azure SQL logo

Azure SQL

Databases

Intelligent, scalable cloud database service from Microsoft

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: Azure SQL ecosystem lock-in limits flexibility compared to open-source or multi-cloud solutions; 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: Azure SQL covers Intelligent Performance, EMQX covers Erlang clustering.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Azure SQL and EMQX actually diverge.

Attributes where Azure SQL and EMQX differ
AttributeAzure SQLEMQX
Pricing modelUnknownPer month by connection and session volume
PlatformsCloud (Microsoft Azure)Linux, Docker, Kubernetes, Cloud, macOS
Founded1975Unknown

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 Azure SQL

  • Intelligent Performance
  • Advanced Security
  • Hyperscale
  • Serverless Compute
  • Geo-replication
  • Automatic Tuning
  • Built-in AI
  • Power BI

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.

Azure SQL

  • Transaction processingnot EMQX
  • Data storagenot EMQX
  • Application backendnot EMQX
  • Reportingnot EMQX
  • Data analyticsnot EMQX

EMQX

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

Where each one falls short

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

Azure SQL

  • Ecosystem lock-in limits flexibility compared to open-source or multi-cloud solutions
  • Managed service reduces control over database configuration and optimization tuning
  • Pricing complexity with consumption-based model can be unpredictable at scale
  • Less operational depth compared to Amazon RDS for advanced scaling scenarios
  • Azure PostgreSQL is less compelling than dedicated PostgreSQL providers outside Azure ecosystem

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

Azure SQL

Free

No published plan breakdown. See the Azure SQL 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 Azure SQL if

  • You need intelligent performance.
  • You want to start without paying.
  • You work on Cloud (Microsoft Azure).
  • You also want advanced security.
Azure SQL 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 Azure SQL or EMQX better?
Neither clearly leads. Azure SQL 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, Azure SQL or EMQX?
Azure SQL starts at Free and EMQX at Free.
Does Azure SQL or EMQX run on more platforms?
Azure SQL runs on Cloud (Microsoft Azure). EMQX runs on Linux, Docker, Kubernetes, Cloud, macOS.
Can I use Azure SQL for free?
Both have a free tier, so you can try either at no cost before committing.
What is Azure SQL best used for?
Azure SQL is most often used for transaction processing, data storage, application backend, reporting. Of those, transaction processing and data storage are not what EMQX is typically brought in for.
What can Azure SQL do that EMQX cannot?
Azure SQL covers Intelligent Performance, Advanced Security, Hyperscale, Serverless Compute. EMQX covers Erlang clustering, MQTT 5.0 and QUIC, Rule engine, Data integration sinks.

Answered from the vendors’ own pages

Azure SQL: Does Azure SQL Database offer a free tier?

Yes, Azure SQL Database includes a permanent free tier that provides 100,000 vCore seconds, 32 GB of data storage, and 32 GB of backup storage per month. This free tier is available for the lifetime of any Azure subscription with no expiration.

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.

Azure SQL: What pricing models does Azure SQL Database support?

Azure SQL Database offers consumption-based pricing where you pay for resources used, with no long-term commitments required. Database Savings Plans launched in March 2026 allow committing to a fixed hourly amount and save up to 35% across Azure database services.

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.

Azure SQL: Is Azure SQL Database compatible with on-premises SQL Server?

Yes, Azure SQL Database shares the same Database Engine as on-premises SQL Server. Existing databases maintain their compatibility level and continue to work after upgrades. Azure SQL Managed Instance provides even broader SQL Server compatibility dating back to SQL Server 2008.

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.

Azure SQL: What high availability features does Azure SQL Database provide?

Azure SQL Database provides automatic backups, geo-replication for disaster recovery, failover groups for automatic failover, and zone redundancy for enhanced availability. The service maintains a 99.99% availability SLA for Business Critical tier.

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.

Azure SQL: Can I use AI features with Azure SQL Database?

Yes, Azure SQL Database includes Copilot for database tasks, Intelligent Applications support, REST API endpoints for building applications, and GraphQL endpoints for modern app development.

Source
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