Softwr

Cloud · head to head

Fly.io vs Kustomize

Fly.io logo

Fly.io

Cloud

Deploy web applications globally

From
$29/month
Rated
-
Full reviewWebsite
Kustomize logo

Kustomize

Cloud

Template-free customisation of Kubernetes YAML

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only Kustomize has a free tier, so it costs nothing to try first.
  • Each has a real cost: 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; Kustomize no packaging or distribution story, which is exactly what Helm charts provide
  • They diverge on capability: Fly.io covers Global deployment, Kustomize covers Overlay patching.

Where they differ

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

Attributes where Fly.io and Kustomize differ
AttributeFly.ioKustomize
Starting price$29/monthFree
Pricing modelusage-basedOpen source, no licence fee
Free tierNoYes
PlatformsWeb, Api, DockerKubernetes, Linux, macOS, Windows
Founded2020Unknown

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 Fly.io

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

Only in Kustomize

  • Overlay patching
  • No templating language
  • Built into kubectl
  • Generators

What people use each for

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

Fly.io

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

Kustomize

  • Managing dev, staging and production variants of the same manifestsnot Fly.io
  • Keeping manifests readable and directly applyable rather than templatednot Fly.io
  • Patching third-party manifests without forking themnot Fly.io

Where each one falls short

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

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

Kustomize

  • No packaging or distribution story, which is exactly what Helm charts provide
  • Deeply nested overlays become hard to follow, and reasoning about the final output requires building it
  • No release lifecycle: nothing tracks what is installed or supports rollback the way Helm does
  • Patch syntax is fiddly for anything beyond simple field replacement

Pricing, plan by plan

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

Kustomize

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

Which should you pick?

Choose Fly.io if

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

Choose Kustomize if

  • You need overlay patching.
  • You want to start without paying.
  • You work on Kubernetes, Linux, macOS, Windows.
  • You also want no templating language.
Kustomize review

Questions people ask

Is Fly.io or Kustomize better?
Neither clearly leads. Fly.io starts at $29/month and Kustomize at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Fly.io or Kustomize?
Kustomize has a free tier; the other does not. Paid plans start at $29/month for Fly.io and Free for Kustomize.
Does Fly.io or Kustomize run on more platforms?
Fly.io runs on Web, Api, Docker. Kustomize runs on Kubernetes, Linux, macOS, Windows.
Can I use Kustomize for free?
Yes. Kustomize has a free tier, so you can try it without paying. Fly.io starts at $29/month.
What is Fly.io best used for?
Fly.io is most often used for deploying containerised applications close to users across regions, running full stack apps and databases on managed machines. Of those, deploying containerised applications close to users across regions and running full stack apps and databases on managed machines are not what Kustomize is typically brought in for.
What can Fly.io do that Kustomize cannot?
Fly.io covers Global deployment, Docker support, Postgres databases, Redis support. Kustomize covers Overlay patching, No templating language, Built into kubectl, Generators.

Answered from the vendors’ own pages

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
Kustomize: Is Kustomize free?

Yes, open source and part of the Kubernetes project.

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
Kustomize: Kustomize or Helm?

Kustomize patches plain YAML and keeps bases readable; Helm templates and packages applications with a release lifecycle. Many teams use both — Helm to install third-party charts, Kustomize to patch them.

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
Kustomize: Do I need to install Kustomize?

No. It is built into kubectl, available through kubectl apply -k.

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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