There’s nothing quite as adventurous in all of IT as spending months building an application that depends on a third-party API for its success. For the most part, developers usually don’t know for sure how much stress the IT infrastructure supporting any given API can stand. If their application is wildly successful, it could suddenly slow to a crawl when that third-party API gets overwhelmed by requests.
Trading systems have historically been the province within large financial institutions that as “master of the universe” controlled trillions of dollars in equity. They did this by essentially locking up access to transaction engines and applications that enable most of the trading that takes place on Wall Street and other exchanges across the globe.