Ethfinex Trustless serves as a gateway from user’s wallet directly into the centralised Ethfinex and Bitfinex order-books. This gives the user of Trustless an opportunity to trade on an ERC20 DEX with industry unmatched liquidity.
However, some of the pairs on the centralised exchanges are traded against fiat money, e.g. USD. Unfortunately, fiat money cannot be stored on Ethereum wallets like Metamask.
The implemented solution is to mirror the XXX/USD orderbook, but to use the ERC20 Tether (USDT) on the Trustless side to match and settle the orders, while keeping the fiat USD on the centralised side. This allows the user of USDT to match orders created using fiat USD and vice versa.
However the exchange rate of USDT/USD is almost never 1:1, so we adjusted the XXX/USDT price on Trustless by the current USDT/USD exchange rate. The price of the pair on Trustless therefore appears to be different from the centralised orderbook, but it is effectively the same.
You can read more technical overview of this mechanism at our API documentation page.