Overview

PAX is a matching engine and co-located trading facility on a single chip.

PAX offers ultra-low latency market access through its λ API and networked order entry by its limit order API. λ programs are small expressions of trading logic enabling nanosecond-scale order entry in response to local and remote market events.

Co-located trading: on-chip vs. legacy

Systematic traders co-locate their servers in physical proximity to the matching engine [1]. Co-location reduces round-trip latency, which means the systematic strategy receives information faster and its resulting sends arrive back at the matching engine sooner. Today’s fastest state-of-the-art markets can provide a round-trip time [2] of approximately 20 µs; after receipt of information, a trader’s algorithm must respond on a nanosecond time scale to remain competitive.

PAX co-locates trading decision logic on the same chip as the core matching algorithm. This gives PAX the lowest round-trip latency of any market for any financial instrument, including traditional markets (NYSE, NASDAQ, Deutsche Börse, LSE) and crypto markets (Binance, OKX, Bybit, EDX Markets, Crossover Markets); see Architecture.

Note 1. The matching engine implements the core algorithm of an electronic trading venue: it matches buyers with sellers in price-time priority.

Note 2. See, e.g., Insights into Trading System Dynamics: Deutsche Börse’s T7 (link).

Account types and API access

PAX offers two account types: free tier and λ tier.

	Fees	Rebates	HTTPS API access	λ API access
Free tier	No	When paired with λ	Yes	No
λ tier	Yes	No	Yes	Yes

Every PAX participant has access to both account types with free tier as the default. Use of the λ API is fee-based and opt-in.

Free tier rebates

Free tier accounts are not charged a fee for trading.

Category	Counterparty	Rebate
Maker or Taker	λ tier	1/2 of λ fee
Maker or Taker	Free tier	No rebate

λ tier fees

Category	Counterparty	Fee
Maker	λ or free tier	1/4 of spread
Taker	λ or free tier	0.5 bps

For further details, including fee calculations and maximums, please see our fees and rebates docs page.