An order matching engine is the software at the core of a trading venue that pairs buy and sell orders according to a defined set of rules. The most common rule is price-time priority: better prices are matched first, and among orders at the same price the one entered earliest is filled first.
The engine maintains the order book, executes trades, publishes the resulting prices and passes fills back to participants. In forex there is no single central exchange, so matching happens across many venues and bank platforms, which is one reason quotes differ slightly between brokers. The speed and capacity of a matching engine influence execution quality, especially during economic releases.
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