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Cloud · head to head

Azure Functions vs Cilium

Azure Functions logo

Azure Functions

Cloud

Event-driven serverless compute on Azure

From
Free
Rated
-
Full reviewWebsite
Cilium logo

Cilium

Cloud

eBPF-based networking, observability and security for Kubernetes

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Azure Functions consumption plan free grant is capped at 1 million executions and 400,000 GB-seconds of resource consumption per month per subscription, billed per GB-second beyond that; Cilium requires a recent Linux kernel, which rules out older distributions and some managed environments

Where they differ

Only the attributes on which Azure Functions and Cilium actually diverge.

Attributes where Azure Functions and Cilium differ
AttributeAzure FunctionsCilium
Pricing modelusage-basedOpen source, no licence fee
PlatformsWebKubernetes, Linux

Identical on both: starting price (Free), free tier (Yes), 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 Azure Functions

Nothing recorded that Cilium does not also cover.

Only in Cilium

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

What people use each for

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

Azure Functions

  • Event-driven computingnot Cilium
  • Serverless application backendnot Cilium
  • Scalable API endpointsnot Cilium

Cilium

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

Where each one falls short

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

Azure Functions

  • Consumption plan free grant is capped at 1 million executions and 400,000 GB-seconds of resource consumption per month per subscription, billed per GB-second beyond that
  • The newer Flex Consumption plan's free grant is smaller still, at 250,000 executions and 100,000 GB-seconds per month
  • Premium plan avoids per-execution charges but bills continuously for allocated core seconds and memory regardless of invocation volume
  • Memory is rounded up to the nearest 128 MB and execution time to the nearest 1 ms for billing, so small overages round upward

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

Pricing, plan by plan

Azure Functions

Free
  • Consumption Plan$null/month
    • 1 million requests free monthly
    • 400,000 GB-seconds free monthly
    • Billed per second and executions
  • Flex Consumption Plan$null/month
    • 250,000 executions free monthly
    • 100,000 GB-seconds free monthly
    • Event-driven scaling
  • Premium Plan$null/month
    • No execution charges
    • At least one instance required
    • Includes automatic scaling and VNET access

Cilium

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

Which should you pick?

Choose Azure Functions if

  • You want to start without paying.
Azure Functions review

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

Questions people ask

Is Azure Functions or Cilium better?
Neither clearly leads. Azure Functions starts at Free and Cilium at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Azure Functions or Cilium?
Azure Functions starts at Free and Cilium at Free.
Does Azure Functions or Cilium run on more platforms?
Azure Functions runs on Web. Cilium runs on Kubernetes, Linux.
Can I use Azure Functions for free?
Both have a free tier, so you can try either at no cost before committing.
What is Azure Functions best used for?
Azure Functions is most often used for event-driven computing, serverless application backend, scalable api endpoints. Of those, event-driven computing and serverless application backend are not what Cilium is typically brought in for.
What can Azure Functions do that Cilium cannot?
Cilium covers eBPF datapath, Identity-based policy, Hubble observability, Sidecar-free mesh.

Answered from the vendors’ own pages

Azure Functions: Does Azure Functions have a free tier?

Yes, Azure Functions includes a monthly free grant of 1 million requests and 400,000 GB-seconds on the Consumption Plan, or 250,000 executions and 100,000 GB-seconds on Flex Consumption.

Source
Cilium: Is Cilium free?

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

Azure Functions: What is Azure Functions' pricing model?

Azure Functions uses usage-based pricing. Consumption plans charge per second of resource consumption and per execution, measured in gigabyte-seconds and rounded to the nearest 128 MB.

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.

Azure Functions: What is the minimum execution time for Azure Functions?

The minimum execution time is 100 milliseconds on Consumption plans. Premium plans charge based on core seconds and allocated memory.

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.

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