Why We Built Relay in Rust: Security, Performance, and Cost

The Language Problem in Systems Engineering

For decades, systems engineers faced an impossible choice: use safe, garbage-collected languages like Python or Java and accept poor performance and high costs, or use unsafe languages like C/C++ and accept constant security vulnerabilities and memory corruption bugs.

This binary choice shaped the entire industry. Companies running mission-critical infrastructure made compromises:

• •Memory safety catastrophes: Buffer overflows, use-after-free bugs, data races—the majority of CVEs in critical infrastructure stem from memory safety issues.
• •GC pauses: Garbage-collected systems suffer unpredictable latency spikes when GC runs, unacceptable for real-time systems.
• •Runtime overhead: VMs, runtimes, and interpreters consume 30-50% more CPU and memory than necessary.
• •Concurrency nightmares: In C/C++, concurrency is error-prone. In garbage-collected languages, it's expensive.

Then Rust arrived. And everything changed.

What Makes Rust Different

Rust doesn't just offer incremental improvements—it's built on fundamentally different principles:

1. Memory Safety Without Garbage Collection

Rust's "ownership" system enforces memory safety at compile-time, not runtime. Every memory access is validated by the compiler:

Compare this to the industry status quo: the Linux kernel (C) has averaged ~3,000-5,000 new vulnerabilities per year. Google estimates 70% are memory safety issues that Rust would prevent entirely.

2. Zero-Cost Abstractions

Rust's abstraction costs nothing at runtime. High-level Rust code compiles to machine code as efficient as hand-written C:

• ✓Iterator adapters: Compile to the same machine code as manual loops
• ✓Trait objects: Use static dispatch by default; dynamic dispatch only when needed
• ✓RAII: Resource cleanup happens at compile-time, not runtime
• ✓Generics: Monomorphized at compile time—no virtual function overhead

The result: Rust code is as fast as C/C++ but dramatically safer and more maintainable.

3. Fearless Concurrency

Concurrency in C/C++ is notoriously error-prone. Race conditions, deadlocks, and data corruption lurk in every concurrent system. Rust's type system makes concurrency a compile-time problem, not a runtime surprise.

Rust for Systems Performance: Real Numbers

Rust doesn't just offer safety—it delivers uncompromising performance. Here's how Rust compares to other systems languages:

Rust is the only language that combines safety, performance, and developer experience. It's C++'s performance with Java's safety, and then goes further by eliminating garbage collection.

Security: The Hidden Cost of Bugs

When you're handling billions of messages and connecting millions of clients, security isn't optional. A single vulnerability can expose your entire user base.

Rust eliminates entire classes of vulnerabilities:

For a real-time communication platform, security is existential. Relay handles encryption keys, user data, and authentication. Rust's safety guarantees mean we can be confident that entire classes of attacks are impossible by construction.

Cost Efficiency: Where Rust Shines

At Stantia Labs, cost efficiency is directly tied to platform viability. Rust enables Relay to achieve 2 billion packets per second with minimal infrastructure:

Rust's Ecosystem: Everything We Need

Early versions of Rust lacked mature libraries. That's no longer true. The ecosystem is now world-class:

• ✓Tokio: The gold-standard async runtime, matching Go's async capabilities with Rust's safety
• ✓io_uring support: Native io_uring bindings let us leverage kernel optimizations directly
• ✓Serialization: serde ecosystem makes data encoding/decoding trivial and efficient
• ✓Cryptography: Ring and RustCrypto provide audited, high-performance crypto primitives
• ✓Testing: Built-in test framework + criterion for benchmarking + property-based testing

Relay's Architecture: Built in Rust

Every layer of Relay is built with Rust and benefits from its guarantees:

The Rust Learning Curve (and Why It's Worth It)

Let's be honest: Rust has a steep learning curve. The borrow checker is notoriously strict. Lifetime annotations can be confusing. Many developers hit a wall initially.

But this is a feature, not a bug.

The "fight with the borrow checker" is actually the compiler helping you think deeply about memory and concurrency. Once you understand Rust's ownership model, you write better code in any language. And in Rust, you know at compile-time that your concurrent code is safe.

For our team at Stantia Labs, the upfront investment in Rust expertise has paid dividends:

• ✓Fewer bugs in production: Memory safety at compile time means fewer runtime surprises
• ✓Faster refactoring: Rust's type system catches refactoring errors that would silently break code in dynamic languages
• ✓Better performance: No surprises from GC pauses or hidden allocations. What you write is what you get.
• ✓Confidence at scale: Running 2 billion packets per second with sub-millisecond latency requires absolute reliability

Rust in Production: The Reality

Rust has moved from "interesting experimental language" to essential infrastructure tool:

• •Linux kernel: Rust is now integrated into the kernel for drivers and filesystem code
• •Cloud providers: AWS, Google, Microsoft all have production Rust services
• •Blockchain: Solana, Polkadot, and other high-performance blockchains are built in Rust
• •Real-time systems: Financial trading systems, robotics, and autonomous vehicles increasingly choose Rust

Why Relay Is Built in Rust

When we started Stantia Labs, we evaluated languages for building Relay:

Rust gave us:

• ✓Confidence: Compiler guarantees eliminate entire classes of bugs before they reach production
• ✓Performance: Control every resource. No surprises from runtime overhead or GC pauses.
• ✓Scalability: io_uring support + async runtime + thread-per-core = 2B packets/sec
• ✓Cost efficiency: 40-60% lower resource consumption than equivalent Java systems
• ✓Security: Memory-safe, thread-safe, and easy to audit

The Future: Rust Becomes Standard

We believe Rust is becoming the standard language for systems programming, not for ideological reasons, but for practical ones:

• •It's the only language that doesn't force you to choose between safety and performance
• •Companies saving 40-60% on infrastructure costs will inevitably standardize on it
• •Security-conscious organizations will adopt it to eliminate vulnerability classes entirely
• •The ecosystem is maturing rapidly—by 2027, Rust will have libraries for virtually any systems task

Conclusion: The Right Tool for the Right Problem

Relay handles billions of events per second with sub-millisecond latency, serves millions of concurrent clients, and maintains fortress-like security. This is only possible because of Rust.

Rust isn't the right choice for every project. But for systems where performance, safety, concurrency, and cost all matter—where a single bug could cascade into catastrophic failures—Rust is increasingly the only rational choice.

At Stantia Labs, we chose Rust because it let us build the platform we wanted: impossibly fast, incredibly safe, and economically sustainable. Every day, we're grateful for that decision.