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Olex Tkachuk
Olex Tkachuk

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How To Improve React App Performance with SSR and Rust [Part II: Rust Web Server]

Continue creating boosted Server Side Rendering implementation. In the first part we prepared ReactJS Application with SSR script that lets choose the best technologies for our Web Server.

Choosing Tech Stack for the SSR Web server

Rust has the most powerful combination of safety and hight speed for today (you can check out here why - In addition, Actix-web framework is the fastest one according TechEmpower Framework Benchmark.

So, let’s use the best technologies for our forced Web Server.

Setup Rust App

It is easy to setup Rust on your computer - just go to website and install rustup CLI in just one step.

Next step is initialisation a new app. Cargo, Rust package manager can help with it: run cargo init inside repository folder.

The Cargo.toml file for each package is called its manifest. It contains settings and dependencies. New one should look like that:

name = "rust-ssr-webserver"
version = "0.1.0"
authors = ["Alex Tkachuk <>"]
edition = "2018"
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Now we can add our dependencies:


actix-web = { version = "^2.0.0", features = ["rustls"] }
actix-rt = "^1.0.0"
actix-files = "^0.2.1"
env_logger = "^0.7.1"
futures = "^0.3.4"
mime_guess = "^2.0.1"
serde_json = "^1.0.40"
lazy_static = "^1.4.0"
rustls = "^0.16.0"
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Using actix-web is quite easy to create web server. Firstly, we need to read SSL keys for supporting HTTPS and HTTP/2:

let mut config = ServerConfig::new(NoClientAuth::new());
let cert_file = &mut BufReader::new(File::open("cert.pem").unwrap());
let key_file = &mut BufReader::new(File::open("key.pem").unwrap());
let cert_chain = certs(cert_file).unwrap();
let mut keys = rsa_private_keys(key_file).unwrap();

config.set_single_cert(cert_chain, keys.remove(0)).unwrap();
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Be aware of using unwrap() in production - if it fails, the app will crash (panic).

We are ready for actually Web Server code now:

HttpServer::new(|| {
            .service(Files::new("/static", "static"))
                            .to(|| HttpResponse::MethodNotAllowed()),
    .bind_rustls("", config)?
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This line: .service(Files::new("/static", "static") is for serving all static asserts that we created by running npm build:ssr in previous article - (Part I: SSR). For handling HTML-files requests from ReactJs App we need to use .default_service() with serving all routes by using web::resource("") with empty string. The index function is handler for such requests:

async fn index(req: HttpRequest) -> impl Responder {
    let path_req = req.match_info().query("tail").get(1..).unwrap_or_default().trim().clone();
    let path = if path_req.len() == 0 {
    } else {
        match ROUTES.get(path_req) {
            Some(r) => r,
            None => "index"

    match std::fs::File::open(format!("static/{}.html", path)) {
        Ok(mut file) => {
            let mut contents = String::new();
            file.read_to_string(&mut contents).unwrap_or_default();

                .content_type("text/html; charset=utf-8")
                .header("Cache-Control", "no-cache, no-store, max-age=0, must-revalidate")
                .header("pragma", "no-cache")
                .header("x-ua-compatible", "IE=edge, Chrome=1")
        Err(e) => {
            // error handling
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The function implements the routing logic, so our web server can return right HTML file (React server rendered) by a route. The ROUTES constant is basically contains data from routes.json that was generated on React side.

One improvement that you can do for this implementation is using a cash instead of directly reading a file from disk.
Finally, copy folder dist/web to static, obviously, it should be automatic step, and run our Web Server by cargo r.

Full example is located in the GitHub repository.

The final article of Server Side Rendering will be about testing performance between this solution vs Node.js

You can check how fast this approach in production by getting Google PageSpeed Insights Performance score for PageSpeed Green website.

Happy coding!

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