Is Envoy or Keil MDK better?

Neither clearly leads. Envoy starts at Free and Keil MDK at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.

Which is cheaper, Envoy or Keil MDK?

Envoy starts at Free and Keil MDK at Free.

Does Envoy or Keil MDK run on more platforms?

Both run on Web, so platform support will not decide this one for you.

Can I use Envoy for free?

Both have a free tier, so you can try either at no cost before committing.

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 Keil MDK is typically brought in for.

What can Envoy do that Keil MDK cannot?

Envoy covers xDS dynamic configuration, Protocol breadth, Filter chain architecture, Observability by default.

Technology · head to head

Envoy vs Keil MDK

Envoy

Technology

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

Full review Website

Keil MDK

Developer Tools

Microcontroller Development Kit for Arm-based devices

From: Free
Free plan: Yes

Full review Website

The short version

Each has a real cost: 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.; Keil MDK pricing for Essential and Professional subscriptions not disclosed on primary site
Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Envoy and Keil MDK actually diverge.

Attributes where Envoy and Keil MDK differ
Attribute	Envoy	Keil MDK
Pricing model	open-source	freemium
Category	Technology	Developer Tools

Identical on both: starting price (Free), free tier (Yes), platforms (Web), user rating (Not yet rated).

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 Keil MDK

Nothing recorded that Envoy does not also cover.

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 Keil MDK
An edge or API gateway that needs per-route retry budgets, circuit breaking and outlier detection rather than round-robin proxyingnot Keil MDK
Migrating traffic between service versions or between a monolith and its replacement, using weighted splits and shadow trafficnot Keil MDK
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 Keil MDK

Keil MDK

Embedded software developmentnot Envoy
ARM microcontroller programmingnot Envoy
Professional development environmentsnot 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.

Keil MDK

Pricing for Essential and Professional subscriptions not disclosed on primary site
Customers must contact Arm Developer Tools store for subscription rates

Pricing, plan by plan

Envoy

Free

No published plan breakdown. See the Envoy review.

Keil MDK

Free

No published plan breakdown. See the Keil MDK review.

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 Keil MDK if

You want to start without paying.

Keil MDK review

Questions people ask

Is Envoy or Keil MDK better?: Neither clearly leads. Envoy starts at Free and Keil MDK at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Envoy or Keil MDK?: Envoy starts at Free and Keil MDK at Free.
Does Envoy or Keil MDK run on more platforms?: Both run on Web, so platform support will not decide this one for you.
Can I use Envoy for free?: Both have a free tier, so you can try either at no cost before committing.
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 Keil MDK is typically brought in for.
What can Envoy do that Keil MDK cannot?: Envoy covers xDS dynamic configuration, Protocol breadth, Filter chain architecture, Observability by default.

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.

Keil MDK: Does Keil MDK have a free version?

Yes, Keil MDK Community Edition is free for non-commercial projects. Essential and Professional editions are available as monthly or annual subscriptions.

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.

Keil MDK: How much do Keil MDK paid editions cost?

Specific pricing for Essential and Professional editions is not published on the main site. Rates are available from the Arm Developer Tools store or by contacting Arm sales.

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.

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.

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.

Envoy vs Keil MDK

Envoy

Keil MDK

The short version

Where they differ

What each one covers

Only in Envoy

Only in Keil MDK

What people use each for

Envoy

Keil MDK

Where each one falls short

Envoy

Keil MDK

Pricing, plan by plan

Envoy

Keil MDK

Which should you pick?

Choose Envoy if

Choose Keil MDK if

Questions people ask

Answered from the vendors’ own pages

Related pages

More on Envoy

More on Keil MDK

Keep looking

Other head to heads