The FIX API has existing software that uses FIX for order management. The Financial Information eXchange is a standard protocol that can be used to enter orders, submit or cancel requests, and receive fills. The GDAX API provides access to a continuous first-come, first-serve order book. Orders are executed in price-time priority as received by the matching engine and includes; Funding, Margin Transfer, Position, Deposits, Withdrawals and more. GDAX is a Global Digital Asset Exchange that offers the ability to trade digital currencies like Bitcoin, Ethereum, and more on a regulated U.S. based exchange.