Why We Rewrote Our Core in Rust

Last quarter, we made the decision to rewrite Pied Piper's compression core from C to Rust. Here's why, and what we learned.

#The Problem with C

Our C codebase worked. It was fast. But we had problems:

1. Memory bugs - Despite careful coding, we'd find buffer overflows in edge cases
2. Concurrency issues - Data races that only manifested under heavy load
3. Maintenance burden - New engineers took months to become productive

The final straw was a production incident caused by a use-after-free bug that our tests didn't catch.

#Why Rust?

Rust gives us:

fn compress_chunk(data: &[u8]) -> Result<Vec<u8>, CompressionError> {
    let mut output = Vec::with_capacity(data.len());

    // The borrow checker ensures we can't accidentally
    // use `data` after it's been moved or freed

    for chunk in data.chunks(BLOCK_SIZE) {
        output.extend(process_block(chunk)?);
    }

    Ok(output)
}

• Memory safety without garbage collection
• Fearless concurrency - The compiler catches data races
• Zero-cost abstractions - High-level code that compiles to efficient assembly

#The Migration

We didn't rewrite everything at once. Our approach:

1. Wrap existing C code with Rust FFI
2. Rewrite one module at a time
3. Benchmark constantly to ensure no regression
4. Delete C code only after Rust replacement is proven

#Results

The performance improvement surprised us—turns out the borrow checker enabled optimizations we were afraid to do in C.

#Lessons

1. Rewrites are risky, but sometimes necessary
2. Incremental migration beats big-bang
3. Rust's learning curve is worth it for systems code