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Databases · head to head

Apache Flink vs Eclipse Mosquitto

Apache Flink logo

Apache Flink

Databases

Stateful stream processing at scale

From
Free
Rated
-
Full reviewWebsite
Eclipse Mosquitto logo

Eclipse Mosquitto

Networking

Small, EPL-licensed MQTT broker that runs on hardware other brokers cannot

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Apache Flink genuinely difficult: event time, watermarks and state backends are a real conceptual load before anything works; Eclipse Mosquitto there is no clustering: Mosquitto is a single process, so high availability means building your own failover and accepting session loss on switchover.
  • They diverge on capability: Apache Flink covers Event-time processing, Eclipse Mosquitto covers MQTT 5.0 support.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Apache Flink and Eclipse Mosquitto actually diverge.

Attributes where Apache Flink and Eclipse Mosquitto differ
AttributeApache FlinkEclipse Mosquitto
Pricing modelOpen source, no licence fee; managed services billed separatelyOpen source, no licence fee
PlatformsLinux, Kubernetes, Docker, Self-hostedLinux, Windows, macOS, Docker
CategoryDatabasesNetworking

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

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 Apache Flink

  • Event-time processing
  • Exactly-once state
  • Batch and stream
  • SQL interface

Only in Eclipse Mosquitto

  • MQTT 5.0 support
  • Very small footprint
  • Bridging
  • WebSockets listener
  • Command line clients
  • Dynamic security plugin

What people use each for

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

Apache Flink

  • Real-time aggregations and dashboards computed over an event streamnot Eclipse Mosquitto
  • Fraud and anomaly detection where patterns span a time windownot Eclipse Mosquitto
  • Joining two live streams where events arrive out of ordernot Eclipse Mosquitto

Eclipse Mosquitto

  • A home or building automation stack where the broker must run on the same small computer as everything elsenot Apache Flink
  • An industrial gateway that buffers local telemetry and bridges selected topics to a cloud brokernot Apache Flink
  • Local development and testing of MQTT clients without provisioning a cloud IoT servicenot Apache Flink
  • An air-gapped deployment where a broker with no licence server and no phone-home behaviour is a requirementnot Apache Flink

Where each one falls short

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

Apache Flink

  • Genuinely difficult: event time, watermarks and state backends are a real conceptual load before anything works
  • Operationally heavy — job managers, task managers, checkpoint storage and state size are all yours to run and tune
  • State grows with the workload, and large state changes recovery time and cost significantly
  • Overkill where a scheduled batch job would answer the same question

Eclipse Mosquitto

  • There is no clustering: Mosquitto is a single process, so high availability means building your own failover and accepting session loss on switchover.
  • Persistence is a local file rather than a replicated store, so a disk failure or an unclean shutdown can lose retained messages and queued QoS traffic.
  • Practical capacity is a few thousand concurrent clients on typical hardware, so a growing device fleet eventually forces a migration to a clustered broker.
  • The Eclipse Public Licence is weak copyleft rather than permissive, which some legal teams treat as a blocker when embedding the broker in a shipped commercial product.
  • There is no commercial support to buy from the project, so production incidents rely on community mailing lists or on paying a third party who happens to know the codebase.

Pricing, plan by plan

Apache Flink

Free
  • Apache FlinkFree
    • Full functionality
    • Self-hosted
    • No usage limits

Eclipse Mosquitto

Free
  • Eclipse MosquittoFree
    • Eclipse Public License 2.0 with Eclipse Distribution Licence
    • MQTT 5.0, 3.1.1 and 3.1
    • No client or message limits beyond your hardware

Which should you pick?

Choose Apache Flink if

  • You need event-time processing.
  • You want to start without paying.
  • You work on Linux, Kubernetes, Docker, Self-hosted.
  • You also want exactly-once state.
Apache Flink review

Choose Eclipse Mosquitto if

  • You need mqtt 5.0 support.
  • You want to start without paying.
  • You work on Linux, Windows, macOS, Docker.
  • You also want very small footprint.
Eclipse Mosquitto review

Questions people ask

Is Apache Flink or Eclipse Mosquitto better?
Neither clearly leads. Apache Flink starts at Free and Eclipse Mosquitto at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Apache Flink or Eclipse Mosquitto?
Apache Flink starts at Free and Eclipse Mosquitto at Free.
Does Apache Flink or Eclipse Mosquitto run on more platforms?
Apache Flink runs on Linux, Kubernetes, Docker, Self-hosted. Eclipse Mosquitto runs on Linux, Windows, macOS, Docker.
Can I use Apache Flink for free?
Both have a free tier, so you can try either at no cost before committing.
What is Apache Flink best used for?
Apache Flink is most often used for real-time aggregations and dashboards computed over an event stream, fraud and anomaly detection where patterns span a time window, joining two live streams where events arrive out of order. Of those, real-time aggregations and dashboards computed over an event stream and fraud and anomaly detection where patterns span a time window are not what Eclipse Mosquitto is typically brought in for.
What can Apache Flink do that Eclipse Mosquitto cannot?
Apache Flink covers Event-time processing, Exactly-once state, Batch and stream, SQL interface. Eclipse Mosquitto covers MQTT 5.0 support, Very small footprint, Bridging, WebSockets listener.

Answered from the vendors’ own pages

Apache Flink: Is Apache Flink free?

Yes, open source under the Apache Software Foundation. Managed services such as Amazon Managed Service for Apache Flink are billed separately.

Eclipse Mosquitto: Can Mosquitto be clustered?

No. It is a single process. High availability requires an external failover arrangement you build yourself.

Apache Flink: Flink or Kafka?

They are complementary rather than alternatives. Kafka moves and stores events; Flink computes over them with windowing, joins and durable state.

Eclipse Mosquitto: What licence is it?

Eclipse Public License 2.0 alongside the Eclipse Distribution License, a weak copyleft rather than a permissive licence.

Apache Flink: What is event-time processing?

Computing based on when an event actually occurred rather than when it arrived. It is what makes results correct when data is late or out of order, and it is the main reason Flink is harder than it looks.

Eclipse Mosquitto: How many clients can it handle?

A few thousand concurrent connections on ordinary hardware; beyond that, use a clustered broker.

Eclipse Mosquitto: Does it support MQTT 5?

Yes, along with 3.1.1 and 3.1.

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