How WebAssembly Complements Ruby on Rails #

When working with Ruby on Rails, performance concerns often arise—particularly when handling real-time updates, background processing, or CPU-intensive operations. While Rails is excellent for handling business logic, ActiveRecord queries, and web requests, it’s not always the best tool for high-performance computing.

WebAssembly (WASM) fills this gap by extending Rails applications with native-like speed. Instead of relying on JavaScript or background jobs for every computation-heavy task, we can offload performance-intensive logic to WebAssembly while keeping the benefits of Hotwire, Turbo Streams, and Solid Trifecta (SolidQueue, SolidCache, SolidCable).

Rails Strengths and Limitations #

Before we discuss WebAssembly’s role in Rails apps, let’s acknowledge what Rails does well and where it struggles:

✅ Strengths:

• Rapid development with convention over configuration
• Robust ORM with ActiveRecord
• Real-time features with Turbo Streams & Stimulus
• Scalable background job processing (Sidekiq, SolidQueue)

🚨 Limitations:

• Single-threaded request handling (can become slow under CPU-heavy tasks)
• Ruby’s interpreted nature means slower performance than compiled languages
• Expensive computations (e.g., image processing, AI tasks) require external services

WebAssembly does not replace Rails but rather enhances it. It allows us to:

• Run high-performance code alongside Rails
• Execute CPU-heavy operations inside the browser instead of overloading the Rails server
• Enable real-time computations directly in Turbo Streams

Example: WebAssembly for Real-Time Computation in a Rails App #

Imagine you are building a real-time analytics dashboard using Rails 8 and Turbo Streams. You need to process large datasets dynamically in the browser without making repeated AJAX requests to the Rails backend.

Without WebAssembly, you would likely use JavaScript like this:

function calculateSum(data) {
    return data.reduce((sum, num) => sum + num, 0);
}

console.time("JS Calculation");
console.log(calculateSum(new Array(1000000).fill(5)));
console.timeEnd("JS Calculation");

This approach works but struggles with large datasets.

Now, let’s move this calculation to WebAssembly using Rust:

#[wasm_bindgen]
pub fn calculate_sum(numbers: Vec<u32>) -> u32 {
    numbers.iter().sum()
}

Once compiled into WebAssembly, this Rust function executes significantly faster than JavaScript. It allows Rails applications to offload computations to the browser while keeping the Rails backend responsive.

By integrating WebAssembly into Rails 8, we can improve response times, reduce server load, and optimize Turbo Streams interactions.