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EngineeringNov 28, 202412 min read

Why We Rebuilt Our Entire Build System in Rust

We were hitting the limits of our Node.js based build system. Here is how we migrated 500k lines of code to Rust and improved build times by 10x.

A
Alex Chen
Principal Engineer

When we first started ViberzFix, our build system was a collection of Node.js scripts held together by npm scripts and a lot of hope. It worked well enough for our small team, but as we grew to support thousands of developers, the cracks started to show.

The Breaking Point

Our build times had grown from seconds to minutes. What was once a tight feedback loop became a frustrating wait. Engineers started batching changes instead of iterating quickly, and our velocity suffered.

The fastest code is code that doesn't run. The second fastest is code written in a systems language.

Why Rust?

We evaluated several options: Go, Zig, and even sticking with Node.js but optimizing harder. Rust won for several reasons:

  • Zero-cost abstractions let us write high-level code without sacrificing performance
  • The type system catches entire categories of bugs at compile time
  • Excellent tooling with cargo and rust-analyzer
  • Growing ecosystem for build tools (see: Turbopack, SWC)

The Migration Strategy

We didn't rewrite everything at once. Instead, we identified the hottest paths in our build pipeline and replaced them incrementally. First, the file watcher. Then, the dependency resolver. Finally, the bundler itself.

rust
fn main() {
    let start = Instant::now();
    
    // Optimizing build pipeline...
    Builder::new()
        .parallel(true)
        .incremental(true)
        .run();
    
    println!("✨ Done in {}ms", start.elapsed().as_millis());
}

The Results

After six months of careful migration, our build times dropped from 4 minutes to under 25 seconds. Cold builds that used to take 10 minutes now complete in under a minute. But the real win wasn't just speed—it was reliability.

Our new build system is deterministic. Given the same inputs, it produces the exact same outputs, every time. This eliminated an entire class of "works on my machine" bugs that had plagued us for years.