Softwr

Cloud · head to head

Flux vs Fly.io

Flux logo

Flux

Cloud

GitOps continuous delivery for Kubernetes

From
Free
Rated
-
Full reviewWebsite
Fly.io logo

Fly.io

Cloud

Deploy web applications globally

From
$29/month
Rated
-
Full reviewWebsite

The short version

  • Only Flux has a free tier, so it costs nothing to try first.
  • Each has a real cost: Flux no user interface of its own: observing what Flux is doing means CLI or a third-party dashboard; Fly.io egress is priced by destination region, from $0.02 per GB in North America and Europe to $0.12 per GB for Africa and India, so the same traffic costs six times more depending on where users are
  • They diverge on capability: Flux covers Git as source of truth, Fly.io covers Global deployment.

Where they differ

Only the attributes on which Flux and Fly.io actually diverge.

Attributes where Flux and Fly.io differ
AttributeFluxFly.io
Starting priceFree$29/month
Pricing modelOpen source, no licence feeusage-based
Free tierYesNo
PlatformsKubernetes, LinuxWeb, Api, Docker
FoundedUnknown2020

Identical on both: user rating (Not yet rated), category (Cloud).

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 Flux

  • Git as source of truth
  • Pull-based delivery
  • Helm and Kustomize support
  • Automated image updates

Only in Fly.io

  • Global deployment
  • Docker support
  • Postgres databases
  • Redis support
  • Auto-scaling
  • Health checks
  • Backups
  • Monitoring

What people use each for

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

Flux

  • Removing cluster credentials from CI systemsnot Fly.io
  • Keeping many clusters consistent with a single declared statenot Fly.io
  • Automatically correcting configuration drift rather than discovering it laternot Fly.io

Fly.io

  • Deploying containerised applications close to users across regionsnot Flux
  • Running full stack apps and databases on managed machinesnot Flux

Where each one falls short

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

Flux

  • No user interface of its own: observing what Flux is doing means CLI or a third-party dashboard
  • Debugging a stuck reconciliation is harder than reading a pipeline log, because failure is asynchronous
  • Everything must be in Git, which is awkward for secrets and needs a sealed-secrets or external-secrets approach
  • GitOps is a workflow change, not just a tool, and teams used to imperative deploys find the adjustment real

Fly.io

  • Egress is priced by destination region, from $0.02 per GB in North America and Europe to $0.12 per GB for Africa and India, so the same traffic costs six times more depending on where users are
  • Stopped machines still bill at $0.15 per GB of root filesystem a month, so a paused service is not a free one
  • Volumes are billed on provisioned capacity rather than usage, at $0.15 per GB a month
  • Reservation discounts of 40% require paying a year up front, from $36 to $1,440
  • Fly Kubernetes is a separate $75 a month per cluster
  • Dedicated IPv4 addresses are $2 a month each

Pricing, plan by plan

Flux

Free
  • FluxFree
    • Full functionality
    • No usage limits
    • Community support

Fly.io

$29/month
  • Pay-as-You-Go$null/mo
    • Micro VMs and persistent storage charged by usage
    • FlyCTL CLI
    • Unlimited users and organizations
  • Serious Support$29/month
    • Access to dedicated engineering team
    • All Pay-as-You-Go features
  • Machine Reservation Blocks$null/mo
    • 40% discount on machine usage
    • Requires upfront payment for savings
  • Compliance Package$99/month
    • HIPAA compliance
    • BAAs
    • SOC2 documentation

Which should you pick?

Choose Flux if

  • You need git as source of truth.
  • You want to start without paying.
  • You work on Kubernetes, Linux.
  • You also want pull-based delivery.
Flux review

Choose Fly.io if

  • You need global deployment.
  • You work on Web, Api, Docker.
  • You also want docker support.
Fly.io review

Questions people ask

Is Flux or Fly.io better?
Neither clearly leads. Flux starts at Free and Fly.io at $29/month, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Flux or Fly.io?
Flux has a free tier; the other does not. Paid plans start at Free for Flux and $29/month for Fly.io.
Does Flux or Fly.io run on more platforms?
Flux runs on Kubernetes, Linux. Fly.io runs on Web, Api, Docker.
Can I use Flux for free?
Yes. Flux has a free tier, so you can try it without paying. Fly.io starts at $29/month.
What is Flux best used for?
Flux is most often used for removing cluster credentials from ci systems, keeping many clusters consistent with a single declared state, automatically correcting configuration drift rather than discovering it later. Of those, removing cluster credentials from ci systems and keeping many clusters consistent with a single declared state are not what Fly.io is typically brought in for.
What can Flux do that Fly.io cannot?
Flux covers Git as source of truth, Pull-based delivery, Helm and Kustomize support, Automated image updates. Fly.io covers Global deployment, Docker support, Postgres databases, Redis support.

Answered from the vendors’ own pages

Flux: Is Flux free?

Yes, open source and CNCF-graduated.

Fly.io: Is there a free tier for Fly.io?

Fly.io does not advertise a free tier. The base plan is pay-as-you-go with usage-based pricing for Micro VMs and persistent storage. All users get FlyCTL CLI, unlimited organizations, private networking, SSO, ACLs, and scoped tokens.

Source
Flux: Flux or Argo CD?

Both implement GitOps. Argo CD ships a strong web UI and is often preferred for visibility; Flux is more modular and composes as controllers, which suits platform teams.

Fly.io: How much does Fly.io Serious Support cost?

Serious Support costs 29 USD per month and provides access to a dedicated engineering team while maintaining all pay-as-you-go features for Micro VMs and storage.

Source
Flux: Why is pull-based safer?

Because the cluster reaches out to Git rather than CI reaching into the cluster. No external system needs write credentials to production.

Fly.io: What does Fly.io Compliance Package include?

The Compliance Package is 99 USD per month and includes HIPAA compliance, BAAs, and SOC2 documentation for organizations requiring compliance certifications.

Source
Fly.io: Does Fly.io offer discounts for upfront commitment?

Yes, Fly.io offers Machine Reservation Blocks with 40% discount on machine usage. This requires upfront payment but applies savings on infrastructure costs.

Source
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