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Cloud · head to head

Cilium vs Fly.io

Cilium logo

Cilium

Cloud

eBPF-based networking, observability and security 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 Cilium has a free tier, so it costs nothing to try first.
  • Each has a real cost: Cilium requires a recent Linux kernel, which rules out older distributions and some managed environments; 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: Cilium covers eBPF datapath, Fly.io covers Global deployment.

Where they differ

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

Attributes where Cilium and Fly.io differ
AttributeCiliumFly.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 Cilium

  • eBPF datapath
  • Identity-based policy
  • Hubble observability
  • Sidecar-free mesh

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.

Cilium

  • Kubernetes networking at a scale where iptables-based CNI performance degradesnot Fly.io
  • Network policy expressed on workload identity rather than fragile IP rulesnot Fly.io
  • Seeing which services actually talk to each other, and what policy is droppingnot Fly.io

Fly.io

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

Where each one falls short

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

Cilium

  • Requires a recent Linux kernel, which rules out older distributions and some managed environments
  • eBPF is genuinely hard to debug when it misbehaves, and the skill is rare on most teams
  • Broad scope — CNI, policy, mesh, observability — means the learning curve covers several domains at once

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

Cilium

Free
  • CiliumFree
    • 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 Cilium if

  • You need ebpf datapath.
  • You want to start without paying.
  • You work on Kubernetes, Linux.
  • You also want identity-based policy.
Cilium 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 Cilium or Fly.io better?
Neither clearly leads. Cilium 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, Cilium or Fly.io?
Cilium has a free tier; the other does not. Paid plans start at Free for Cilium and $29/month for Fly.io.
Does Cilium or Fly.io run on more platforms?
Cilium runs on Kubernetes, Linux. Fly.io runs on Web, Api, Docker.
Can I use Cilium for free?
Yes. Cilium has a free tier, so you can try it without paying. Fly.io starts at $29/month.
What is Cilium best used for?
Cilium is most often used for kubernetes networking at a scale where iptables-based cni performance degrades, network policy expressed on workload identity rather than fragile ip rules, seeing which services actually talk to each other, and what policy is dropping. Of those, kubernetes networking at a scale where iptables-based cni performance degrades and network policy expressed on workload identity rather than fragile ip rules are not what Fly.io is typically brought in for.
What can Cilium do that Fly.io cannot?
Cilium covers eBPF datapath, Identity-based policy, Hubble observability, Sidecar-free mesh. Fly.io covers Global deployment, Docker support, Postgres databases, Redis support.

Answered from the vendors’ own pages

Cilium: Is Cilium free?

Yes, open source and CNCF-graduated. Isovalent sells an enterprise distribution and support.

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
Cilium: What does eBPF change?

It lets Cilium run packet-processing programs inside the kernel instead of relying on iptables rule chains, which behave poorly as the number of services grows.

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
Cilium: Does Cilium replace a service mesh?

It can cover much of what a mesh does without sidecars, though full mesh feature sets still favour Istio or Linkerd.

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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