Multiply that decision by billions and you get the machinery this guide opens up: how financial market structures works, from the matching engine to the moment money actually moves. How financial market structures works at the matching engineEvery exchange runs on the same core algorithm: price-time priority. A market order crossing that gap executes instantly against the best resting order. Market makers and the price of immediacyNobody is obligated to be on the other side of a trade, so the structure pays specialists to volunteer. Market makers quote both sides continuously and earn the spread as compensation for the risk of holding inventory when prices move against them.