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Databases · head to head

Apache Flink vs Windmill

Apache Flink logo

Apache Flink

Databases

Stateful stream processing at scale

From
Free
Rated
-
Full reviewWebsite
Windmill logo

Windmill

Automation Integration

Open-source developer platform for building scripts, workflows, and internal apps

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; Windmill free self-hosted tier caps SSO users at 10 and workspaces at 3, requiring Enterprise for larger teams.
  • They diverge on capability: Apache Flink covers Event-time processing, Windmill covers Script-to-workflow engine.
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which Apache Flink and Windmill actually diverge.

Attributes where Apache Flink and Windmill differ
AttributeApache FlinkWindmill
Pricing modelOpen source, no licence fee; managed services billed separatelyopen-source
PlatformsLinux, Kubernetes, Docker, Self-hostedweb, api, linux, windows, mac
CategoryDatabasesAutomation Integration

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 Windmill

  • Script-to-workflow engine
  • Auto-generated UIs
  • Self-hosted deployment
  • Git sync
  • SSO support
  • Audit logs

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 Windmill
  • Fraud and anomaly detection where patterns span a time windownot Windmill
  • Joining two live streams where events arrive out of ordernot Windmill

Windmill

  • Turning ad-hoc scripts into scheduled jobs and APIsnot Apache Flink
  • Building internal tools from existing Python/TypeScript codenot Apache Flink
  • Self-hosted automation for engineering teamsnot Apache Flink
  • Orchestrating multi-language workflowsnot 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

Windmill

  • Free self-hosted tier caps SSO users at 10 and workspaces at 3, requiring Enterprise for larger teams.
  • Compute unit and seat-based pricing (developer vs. operator seats, worker compute units) adds pricing complexity beyond a flat monthly fee.
  • Email triggers are capped at 100/day on the free tier, limiting event-driven use cases without upgrading.
  • Smaller ecosystem of pre-built integrations compared to more established automation tools like n8n.

Pricing, plan by plan

Apache Flink

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

Windmill

Free
  • Free / Open-sourceFree
    • Unlimited executions
    • Self-hosted deployment
    • Max 10 users with SSO
  • Enterprise$120/month
    • Unlimited executions and workspaces
    • Uncapped SSO seats
    • 24/7 priority support (3-hour response)

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 Windmill if

  • You need script-to-workflow engine.
  • You want to start without paying.
  • You work on web, api, linux, windows, mac.
  • You also want auto-generated uis.
Windmill review

Questions people ask

Is Apache Flink or Windmill better?
Neither clearly leads. Apache Flink starts at Free and Windmill at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Apache Flink or Windmill?
Apache Flink starts at Free and Windmill at Free.
Does Apache Flink or Windmill run on more platforms?
Apache Flink runs on Linux, Kubernetes, Docker, Self-hosted. Windmill runs on web, api, linux, windows, mac.
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 Windmill is typically brought in for.
What can Apache Flink do that Windmill cannot?
Apache Flink covers Event-time processing, Exactly-once state, Batch and stream, SQL interface. Windmill covers Script-to-workflow engine, Auto-generated UIs, Self-hosted deployment, Git sync.

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.

Windmill: What does Windmill cost?

Windmill's Free and Open-source edition is $0/month for self-hosted use with unlimited executions, while Enterprise starts at $120/month with unlimited workspaces and uncapped SSO seats, priced further by developer/operator seats and compute units.

Source
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.

Windmill: Is there a free plan and what are its limits?

The free self-hosted plan supports unlimited executions but caps SSO at 10 users, workspaces at 3, groups/permissions at 4, and email triggers at 100 per day.

Source
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.

Windmill: How is usage metered on Windmill Enterprise?

Enterprise usage is metered through seats (developer seats at $20/month, operator seats at $10/month) and compute units, e.g. $100/month for 2 standard-worker compute units.

Source
Windmill: What happens to a self-hosted Windmill deployment if the company shuts down?

The pricing page addresses this directly as an FAQ topic, noting that self-hosted applications built on the open-source edition can continue running independently of Windmill the company.

Source
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