Polymarket has opened sandbox testing for Nex, a new trading system rewritten from scratch in Rust that is designed to replace its current centralized limit order book. Josh Stevens, Polymarket's vice president of engineering for DeFi, announced the move on X on Nov. 13, with a conditional launch planned for mid-December.
The new engine targets 100,000 commands per second under sustained load, with peak capacity of up to 150,000, compared with the current system's 10,000 per second steady load and 15,000 peak. Stevens said the team began the rewrite in August after concluding the existing infrastructure could not be saved, citing race conditions and inconsistent behavior.
Published internal metrics show dramatic latency improvements: 99th percentile order placement dropped from 1.55 seconds to 3.76 milliseconds, a roughly 412-fold improvement. Cancel order p99 latency fell from 627.92 milliseconds to 3.20 milliseconds, and cancel market order latency fell from 810.16 milliseconds to 5.14 milliseconds. At p95, order placement improved from 341.84 milliseconds to 1.59 milliseconds. The rewritten Rust WebSocket service recorded p99 write latency of 0.099 milliseconds, versus 44.5 to 88.1 milliseconds previously, and platform startup time fell from five minutes to 15 seconds.
Polymarket emphasized that the figures are internal exchange timings, not end-to-end latency, and that end-to-end measurements will follow. Nex has been running in shadow mode alongside the existing exchange for the past week, mirroring production orders so engineers can compare response times, load stability, and matching accuracy. The platform plans four weeks of shadow testing before deciding on deployment in mid-December. The upgrade introduces no breaking changes to requests or responses, preserving compatibility for market makers and builders. WebSocket improvements could be released earlier because they can be deployed separately.
The overhaul follows other infrastructure work, including an in-house indexing upgrade that surfaced some blockchain events up to 14 blocks, or roughly 28 seconds, faster, and a Protocol V2 smart contract overhaul earlier this year.
