Rust vs Ruby: Building an API

2 minute read

I’ve been itching to write this blog post for a while. Now that Rust is 1.0.0-beta the time has come.

Recently i’m trying to learn Rust and dealing with lots of compile-time errors :) As a Rubyist i felt very overwhelmed when i first saw the Rust syntax. But as i started to understand the concepts all the overwhelming feeling is gone and now i’m pretty in love with Rust.

As i’m experimenting with Rust i’d like to try something useful. Building a simple API and seeing how it performs against Ruby. Our simple API will return a JSON response like

{"first_name": "Hello", "last_name": "World"}

Let’s get dirty :)


For both examples i don’t want too much framework overhead that’s why i’m gonna use microframeworks which are pretty close to metal.

First we gonna start with Rust

Rust Application

For Rust implementation we gonna use

Let’s start with creating our project. Since this is not a library we gonna use –bin option.

cargo new rust-json-api --bin
cd rust-json-api

To use nickel we need to modify our Cargo.toml file like below.

name = "rust-json"
version = "0.0.1"
authors = ["Sdogruyol <[email protected]>"]

git = ""

git = ""

rustc-serialize = "*"

And to implement our api here’s our src/ file

#[macro_use] extern crate nickel_macros;
extern crate rustc_serialize;
extern crate nickel;

use std::collections::BTreeMap;
use nickel::{Nickel,HttpRouter};
use rustc_serialize::json::{Json, ToJson};

fn main() {
	let mut server = Nickel::new();

	server.utilize(router! {
			get "**" => |_req, _res| {
				let person = Person{
					first_name: "Hello".to_string(),
					last_name: "World".to_string()

#[derive(RustcDecodable, RustcEncodable)]
	struct Person {
	first_name: String,
	last_name: String,

impl ToJson for Person {
	fn to_json(&self) -> Json {
			let mut map = BTreeMap::new();
			map.insert("first_name".to_string(), self.first_name.to_json());
			map.insert("last_name".to_string(), self.last_name.to_json());

I know that you’re pretty much scared after seeing this code :) Well don’t worry this is a simple JSON API.

To run

cargo run --release

Open your browser and go to http://localhost:9292 to see it yourself :)

That’s it for our Rust implementation.

Ruby Application

For our Ruby application we gonna use cuba because it’s pretty close to Rack.

To create our Cuba application we gonna use cuba-generator.

gem install cuba-generator

Now that we have installed cuba-generator. Let’s create and run our api :)

cuba new ruby-json-api --type api
cd ruby-json-api && rackup

I’m not gonna go into the details of Ruby implementation since it’s pretty easy. You can find the sample application at the links below.

Like the Rust application open your browser and go to http://localhost:9292 to see it in action.


I’ve really wondered how Ruby is gonna perform against Rust and that’s why benchmarked the apps using wrk.

100 connections

wrk -c 100 http://localhost:9292

1000 connections

wrk -c 1000 http://localhost:9292


First of all Rust is really really fast serving nearly 70k RPS which is expected given that it’s a compiled language with great performance.

The most surprising thing is that JRuby is really fast when paired with Rack / Cuba serving nearly 15k RPS which is a great accomplishment.

Lastly MRI serves around 9k RPS on both 100 and 1000 connections. I think the GIL is at fault here.

So Rust or Ruby? Which one do you prefer?

Happy hacking <3

P.S: You can find the sample apps on Github

Update: I’ve reproduced the Ruby benchmarks with RACK_ENV=production variable and saw more than 5x performance increase.

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