Polymarket will rebuild its central limit order book (CLOB) from the ground up after determining that its existing codebase cannot be sustained long-term, VP of Engineering Josh Stevens announced. The decision follows repeated trading disruptions that forced the exchange to halt new orders and switch to cancel-only mode.
The most recent outages were linked to delayed responses when users attempted to read unfilled orders. Stevens characterized the current infrastructure as "full of tech debt" and stated the codebase "can't be saved long-term," noting that attempts to fix individual issues created new problems elsewhere.
Technical Overhaul and Performance Targets
Polymarket will rewrite the CLOB in Rust, a language that provides memory safety without garbage collection. This approach aims to eliminate unpredictable latency spikes that occur under heavy trading loads, as traditional garbage collection can cause periodic system pauses.
The new exchange targets 200,000 orders per second, approximately 15 times Polymarket's current throughput, with potential to scale beyond 400,000 orders per second. Early testing shows 10–20x faster p99 latency compared to the existing system. The engineering team has previously scaled the current system 10x and achieved 3x faster performance, but Stevens indicated the underlying architecture remained the core constraint.
Implementation Timeline
Polymarket plans to run both the existing and new CLOB systems in parallel during development, with the new exchange targeted for deployment in Q4 2026. The company intends to minimize breaking changes for integrators and will communicate any modifications in advance.
The existing CLOB will continue operating and receiving improvements while the Rust-based system is developed. Stevens emphasized the stakes involved: "This is people's money, not a joke."
