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Developer Tools · head to head

Envoy vs Fly.io

Envoy logo

Envoy

Developer Tools

A high-performance L7 proxy written in C++ that is configured by an API rather than a config file, and is usually deployed under a control plane.

From
Free
Free plan
Yes
Visit EnvoyFull review
Fly.io logo

Fly.io

Cloud

Deploy web applications globally

From
$29/month
Free plan
No
Visit Fly.ioFull review

The short version

  • Envoy is free; Fly.io starts at $29/mo.
  • Only Envoy lists xDS dynamic configuration; only Fly.io lists global deployment.
  • Where Fly.io falls short: stopped machines still bill at $0.15 per GB of root filesystem a month, so a paused service is not a free one.
  • Prices and features on this page were last checked on 13 November 2026.

Where they differ

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

Attributes where Envoy and Fly.io differ
AttributeEnvoyFly.io
Starting priceFree$29/month
Pricing modelOpen-sourceUsage-based
Free tierYesNo
PlatformsWebWeb, API, Self-hosted
CategoryDeveloper ToolsCloud

Not yet recorded: founded for Envoy.

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 Envoy

  • xDS dynamic configuration
  • Protocol breadth
  • Filter chain architecture
  • Observability by default
  • Outlier detection
  • Traffic shaping
  • mTLS termination and origination
  • Hot restart

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.

Envoy

  • Acting as the data plane under a service mesh or Gateway API implementation, which is how the overwhelming majority of deployments use itnot Fly.io
  • An edge or API gateway that needs per-route retry budgets, circuit breaking and outlier detection rather than round-robin proxyingnot Fly.io
  • Migrating traffic between service versions or between a monolith and its replacement, using weighted splits and shadow trafficnot Fly.io
  • Standardising observability across a polyglot estate, so that latency, error rates and tracing look the same regardless of the language a service is written innot Fly.io

Fly.io

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

Where each one falls short

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

Envoy

  • The configuration surface is very large and hand-written bootstrap YAML runs to hundreds of lines for routing that Nginx expresses in twenty, which is why nearly every production deployment sits under a control plane and inherits that control plane's constraints as well
  • xDS is the real API and it is not stable in the comfortable sense; the v2 API set was removed outright, resource types continue to be deprecated, and your control plane and Envoy binaries have to be upgraded roughly in step or the proxies stop accepting configuration
  • Extending it properly means writing a C++ filter and building and maintaining your own Envoy binary; the alternatives are Lua, which adds per-request overhead, and proxy-wasm, whose ABI has remained effectively experimental for years with a real performance cost
  • At sidecar density the per-proxy memory and CPU footprint is a measurable share of cluster capacity, since thousands of workloads each carry a full proxy, and this is precisely the cost that has pushed mesh projects towards node-level or ambient architectures
  • There is no single vendor selling support for Envoy itself; you get the community plus control-plane vendors such as Solo.io and Tetrate, so an Envoy-level production bug is your own engineers in a C++ codebase unless a support contract happens to cover it
  • Diagnosing why a request got a particular response involves reading config dumps, the stats endpoint and the RESPONSE_FLAGS codes in access logs rather than a readable error, which is a specific skill you must hire or spend months growing

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

Envoy

Free

No published plan breakdown. See the Envoy review.

Fly.io

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

Which should you pick?

Choose Envoy if

  • You need xds dynamic configuration.
  • You want to start without paying.
  • You also want protocol breadth.
Envoy review

Choose Fly.io if

  • You need global deployment.
  • You work on Web, API, Self-hosted.
  • You also want docker support.
Fly.io review

Questions people ask

Is Envoy or Fly.io better?
Neither clearly leads. Envoy 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, Envoy or Fly.io?
Envoy has a free tier; the other does not. Paid plans start at Free for Envoy and $29/month for Fly.io.
Does Envoy or Fly.io run on more platforms?
Envoy runs on Web. Fly.io runs on Web, API, Self-hosted.
Can I use Envoy for free?
Yes. Envoy has a free tier, so you can try it without paying. Fly.io starts at $29/month.
What is Envoy best used for?
Envoy is most often used for acting as the data plane under a service mesh or gateway api implementation, which is how the overwhelming majority of deployments use it, an edge or api gateway that needs per-route retry budgets, circuit breaking and outlier detection rather than round-robin proxying, migrating traffic between service versions or between a monolith and its replacement, using weighted splits and shadow traffic, standardising observability across a polyglot estate, so that latency, error rates and tracing look the same regardless of the language a service is written in. Of those, acting as the data plane under a service mesh or gateway api implementation, which is how the overwhelming majority of deployments use it and an edge or api gateway that needs per-route retry budgets, circuit breaking and outlier detection rather than round-robin proxying are not what Fly.io is typically brought in for.
What can Envoy do that Fly.io cannot?
Envoy covers xDS dynamic configuration, Protocol breadth, Filter chain architecture, Observability by default. Fly.io covers Global deployment, Docker support, Postgres databases, Redis support.

Answered from the vendors’ own pages

Envoy: Should I run Envoy on its own, or under a control plane?

Almost always under one. Directly authoring xDS or static bootstrap configuration is viable for a handful of routes and becomes unmanageable beyond that. Envoy Gateway, Istio, Contour, Gloo and Consul all exist to generate that configuration for you.

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
Envoy: How does it compare with Nginx or HAProxy?

Envoy is dynamically configured over an API and instrumented far more heavily; Nginx and HAProxy are faster to configure and lighter for straightforward reverse proxying. If you never need to change routing without a reload, Envoy is more machinery than the problem requires.

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
Envoy: What does it cost?

Nothing to licence; it is Apache 2.0 and there is no paid edition. The cost is engineering time and, for most organisations, a commercial control plane or cloud service that packages it.

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
Envoy: Can I write extensions without C++?

You can write Lua filters or proxy-wasm modules in Rust, Go, C++ or AssemblyScript. Both carry per-request overhead compared with a native filter, and the Wasm path has been slower to stabilise than the project originally projected.

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
Envoy: Is it a CNCF project?

Yes, it is a graduated CNCF project licensed under Apache 2.0, which means the trademark and governance sit with the foundation rather than with Lyft or any vendor.

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