Why Rust instead of C++ for the feed handler?

Rust's memory safety without GC and fearless concurrency caught bugs that would have crashed C++ version.

How do you handle feed recovery after disconnect?

Snapshot recovery from ClickHouse with sequence number gap detection.

How does this case study work?

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Reducing Market Data Processing Latency

Executive Summary

A systematic fund's market data feed handler was the latency bottleneck, adding 45μs before strategies could react. Rewriting in Rust with DPDK kernel bypass and lock-free order book reconstruction reduced latency by 82%, enabling new alpha strategies.

Key Outcomes

▹ 82% reduction in feed processing latency (45μs → 8μs)
▹ Handles 10M messages/sec on single core
▹ Enabled 3 new latency-sensitive strategies

Client Situation

The fund's mid-frequency strategies required consistent sub-50μs data delivery. Their feed handler couldn't keep up during volatility spikes.

Key Challenges

⚠ 45μs processing latency eating into available decision window
⚠ Message drops during 10x volume spikes
⚠ Inability to add new instruments without increasing latency

Existing Architecture

C++ feed handler using Linux kernel networking with TCP. Order book reconstruction using STL containers with locks.

Kernel networking stack adding 20-30μs overhead
Lock contention on order book during high update rates
Memory allocations causing unpredictable pauses

Solution Design

Rust feed handler with DPDK for kernel bypass, lock-free order book using crossbeam, and pre-allocated memory pools.

Key Decisions

✓ Use DPDK for direct NIC to userspace packet delivery
✓ Lock-free order book using epoch-based memory reclamation
✓ No-std Rust for deterministic allocation-free path

RustDPDKcrossbeamClickHousegRPC

Implementation

Shadow mode for 6 weeks, comparing rebuilt feed handler against production baseline before cutover.

Phase 1: Phase 1: DPDK Integration
Implemented packet capture and parsing in Rust using DPDK bindings.
Phase 2: Phase 2: Lock-Free Order Book
Built concurrent order book with snapshot capability, zero allocations.
Phase 3: Phase 3: Full Deployment
Replaced existing feed handler across all 50 trading servers.

Technical Challenges

DPDK memory management in Rust

Impact: Huge pages causing cross-language memory safety issues

Resolution: Created safe Rust abstractions over DPDK memory pools

Order book snapshot consistency

Impact: Risk queries seeing inconsistent state during updates

Resolution: Double-buffered snapshots with epoch protection

Results

Feed handler processing latency (P99): Before45μs
After8μs
Improvement82% reduction
Max message rate (single core): Before1.5M/sec
After10M/sec
Improvement6.7x increase
Memory allocations per message: Before3-5
After0
Improvement100% elimination

Lessons Learned

📘 Rust's ownership model caught 12 race conditions in order book logic
📘 DPDK kernel bypass is essential for deterministic sub-10μs processing
📘 Pre-allocated memory pools eliminated GC/alloc pauses entirely

What We Would Do Differently

💡 Use io_uring instead of DPDK for less vendor lock-in
💡 Implement persistent order book snapshots for recovery

Role Relevance

Quant developers with systems programming expertise in Rust and kernel bypass were critical for achieving 8μs deterministic latency.

Critical Skills Demonstrated

Kernel bypass (DPDK/io_uring)Lock-free data structuresRust no_std developmentOrder book reconstruction

Frequently Asked Questions

Why Rust instead of C++ for the feed handler?: Rust's memory safety without GC and fearless concurrency caught bugs that would have crashed C++ version.
How do you handle feed recovery after disconnect?: Snapshot recovery from ClickHouse with sequence number gap detection.