Is Rust Used in High-Frequency Trading Systems?

Mar 15, 2026

Cowrie

Dev @ Bswen

The Question

I’ve been tracking language adoption in high-frequency trading for a few years. C++ has been the undisputed king for decades - every major trading firm built their stack on it. But recently, I’ve noticed more Rust job postings in the HFT space and heard whispers about new services being written in Rust.

This raised a question: Is Rust actually being used in high-frequency trading systems? Or is this just noise from the Rust hype train?

What I Found

The short answer: Yes, Rust is being used in HFT. But it’s not replacing C++ across the board. Instead, it’s carving out specific niches.

I found a Reddit discussion with 62 upvotes that painted a clear picture. The top-voted insights told the real story:

Score	Key Insight
4	”C++ is still deeply entrenched in finance HFT, game engines, and anything latency-critical”
3	”Rust is beloved and growing, but still a somewhat small player in the market”
1	”New low latency services are in rust now”
1	”Programmable network software (on smartnics) and kernel modules are written in C++ or C still”

This matches what I’ve seen in practice. The pattern is clear: C++ dominates existing infrastructure, Rust wins new services.

The Current State of Rust in HFT

Where Rust Is Winning

I’ve observed Rust gaining ground in specific areas:

1. New microservices - When a firm needs a new order routing service or market data handler, Rust is often the first choice
2. Network-facing components - Systems that parse external data benefit from Rust’s memory safety
3. Greenfield projects - Teams starting fresh without legacy constraints often pick Rust

One engineer in the discussion mentioned directly: “New low latency services are in rust now.” This isn’t speculation - it’s happening.

Where C++ Remains Dominant

C++ isn’t going anywhere in HFT. The entrenched position is real:

1. Legacy trading engines - Millions of lines of optimized C++ code that works
2. Kernel modules and drivers - Low-level systems code still uses C/C++
3. SmartNIC programming - Network cards with programmable chips run C/C++
4. Firms with deep C++ expertise - Teams that have spent 20 years optimizing C++ workflows

As one commenter put it: “C++ is still deeply entrenched.” I’ve seen trading firms that would take months just to map out their C++ dependencies. A rewrite isn’t happening.

Performance Considerations

I’ve tested both languages for latency-critical code. Here’s what matters in HFT:

Zero-Cost Abstractions

Both Rust and C++ offer zero-cost abstractions. The Rust iterator chain compiles to the same tight loop as hand-written C++:

rust_loop.rs

// High-level iterator code
let sum: i64 = market_updates
    .iter()
    .filter(|u| u.symbol == target_symbol)
    .map(|u| u.price as i64)
    .sum();

The generated assembly is indistinguishable from:

cpp_loop.cpp

// Hand-written C++ loop
int64_t sum = 0;
for (const auto& u : market_updates) {
    if (u.symbol == target_symbol) {
        sum += u.price;
    }
}

Compile-Time Safety

This is where Rust shines for trading systems. I’ve debugged too many C++ race conditions and use-after-free bugs that only appeared under load in production. Rust catches these at compile time.

For an HFT system where a crash means lost money, this matters:

rust_ownership.rs

fn process_order(order: Order) -> Result<Execution, Error> {
    // Order is owned here - can't be modified elsewhere
    // Compiler ensures no data races
    let validated = order.validate()?;

    // This consumes validated - can't use it again
    Ok(validated.execute())
}

The borrow checker enforces ownership at compile time. No more debugging heisenbugs at 3 AM.

Predictable Latency

HFT systems need predictable latency, not just fast average latency. Rust helps here:

1. No garbage collection - No GC pauses to worry about
2. No hidden allocations - Memory allocations are explicit
3. Control over layout - #[repr(C, packed)] gives C-level control

But C++ has these too. The real difference is safety without sacrificing control.

When to Choose Rust vs C++ for HFT

I use this decision matrix when advising teams:

Factor	Choose Rust	Choose C++
Codebase status	Greenfield project	Extending existing C++ system
Memory safety priority	Parsing external data, network code	Internal computation only
Team expertise	Rust experience available	Deep C++ expertise
Library dependencies	Standard libs sufficient	Need specific C++ libraries
Kernel/driver work	Application layer only	Need kernel modules
Hardware programming	Application logic	SmartNIC/FPGA interfaces
Timeline pressure	Can afford learning curve	Need fastest development
Interop requirements	Standalone service	Must link with C++ libraries

The most common pattern I see: Rust for new services, C++ for existing infrastructure. A hybrid approach works well.

Key Performance Patterns for HFT

Whether you choose Rust or C++, the performance patterns for HFT are similar. Here’s what I’ve found essential:

Lock-Free Data Structures

rust_lockfree.rs

use crossbeam_queue::ArrayQueue;

pub struct OrderQueue {
    // Lock-free queue for passing orders between threads
    // No mutex contention, no priority inversion
    pending: ArrayQueue<Order>,
}

impl OrderQueue {
    pub fn push(&self, order: Order) -> Result<(), Order> {
        self.pending.push(order)
    }

    pub fn pop(&self) -> Option<Order> {
        self.pending.pop()
    }
}

The lock-free approach eliminates priority inversion - critical for trading systems where microseconds matter.

Memory Pooling

Allocating memory during trading hours is a latency sin. I pre-allocate everything:

rust_memory_pool.rs

pub struct OrderPool {
    // Pre-allocated memory for orders
    // No allocations during market hours
    orders: Box<[MaybeUninit<Order>; MAX_ORDERS]>,
    free_list: Vec<usize>,
}

impl OrderPool {
    pub fn acquire(&mut self) -> Option<&mut Order> {
        // Get from pool - no heap allocation
        let idx = self.free_list.pop()?;
        Some(unsafe { self.orders[idx].assume_init_mut() })
    }

    pub fn release(&mut self, idx: usize) {
        // Return to pool for reuse
        self.free_list.push(idx);
    }
}

Cache-Line Alignment

False sharing kills performance in multi-threaded trading systems:

rust_cache_aligned.rs

#[repr(align(64))]
pub struct AlignedCounter {
    // Each counter lives on its own cache line
    // Prevents false sharing between CPU cores
    value: AtomicU64,
}

pub struct TradingCounters {
    orders_received: AlignedCounter,    // Cache line 1
    orders_executed: AlignedCounter,    // Cache line 2
    orders_rejected: AlignedCounter,    // Cache line 3
}

SIMD for Market Data

Processing thousands of price updates per microsecond requires SIMD:

rust_simd.rs

use std::simd::*;

pub fn find_best_bid(prices: &[f64]) -> f64 {
    // Process 4 or 8 prices at once using SIMD
    let chunks = prices.chunks_exact(8);
    let remainder = chunks.remainder();

    let mut max_lanes = chunks.map(|chunk| {
        let lane = f64x8::from_slice(chunk);
        lane.reduce_max()
    });

    // Handle remaining elements
    for &price in remainder {
        max_lanes.push(price);
    }

    max_lanes.into_iter().fold(f64::NEG_INFINITY, f64::max)
}

These patterns apply to both Rust and C++. The language choice matters less than using the right patterns.

A Real-World Example

I recently worked with a trading firm that needed a new market data gateway. Their existing stack was C++ with 15 years of history. They chose Rust for the new service.

Here was their reasoning:

Decision Factors:
- Gateway parses external exchange feeds (memory safety matters)
- Standalone service, no C++ library dependencies
- Team wanted to build Rust expertise
- Latency target: sub-10 microseconds (achievable in both)

Why Rust won:
- Parsing untrusted network data safely
- Fresh service with no legacy integration
- Long-term maintenance concerns
- Hiring for Rust skills

The core order processing looked like this:

rust_order_handler.rs

#[repr(C, packed)]
pub struct OrderUpdate {
    pub symbol_id: u32,
    pub side: u8,
    pub price: i64,
    pub quantity: u64,
    pub timestamp: u64,
}

impl OrderUpdate {
    pub fn parse(data: &[u8]) -> Result<Self, ParseError> {
        if data.len() < std::mem::size_of::<Self>() {
            return Err(ParseError::TooShort);
        }

        // Safe parsing with explicit error handling
        let update: Self = unsafe {
            std::ptr::read_unaligned(data.as_ptr() as *const _)
        };

        // Validate fields
        if update.price <= 0 {
            return Err(ParseError::InvalidPrice);
        }

        Ok(update)
    }

    #[inline(always)]
    pub fn process(&self, book: &mut OrderBook) -> Result<(), TradingError> {
        // Inline for zero function call overhead
        book.update(self.symbol_id, self.side, self.price, self.quantity)
    }
}

The explicit error handling and ownership model caught several bugs during development that would have been hard to debug in C++.

The Adoption Trend

What I see in the industry:

1. Established firms - Keeping C++ cores, adding Rust services at the edges
2. New firms - Building primarily in Rust, with C++ only for specific needs
3. Hybrid shops - Rust for application logic, C++ for kernel/hardware interfaces

The trend is clear but gradual. Rust isn’t replacing C++ overnight. It’s being adopted incrementally where it makes sense.

Summary

Rust is used in high-frequency trading systems, but the picture is nuanced:

• New low-latency services are increasingly written in Rust
• C++ remains entrenched in existing trading infrastructure and kernel-level code
• Memory safety matters for network-facing components that parse external data
• Performance is comparable - both offer zero-cost abstractions and predictable latency
• The trend favors Rust for greenfield projects, C++ for legacy systems

If you’re starting a new HFT service today, Rust should be your default consideration. If you’re maintaining or extending existing C++ infrastructure, stay with C++. The decision is less about raw performance and more about safety, team expertise, and integration requirements.

Final Words + More Resources

My intention with this article was to help others share my knowledge and experience. If you want to contact me, you can contact by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

• 👨‍💻 Reddit r/learnprogramming Discussion
• 👨‍💻 Rust Programming Language
• 👨‍💻 C++ Reference

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!

Comments

Tags:

• performance
• career

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