FIX API
FIX API is FIX Protocol standard designed for real-time, custom institutional interface which pushes up to 250 price updates per second (not available on other APIs). It is their fastest and most popular option. The FIX API Protocol is only available to professional clients.
FIX API using FIX Protocol 4.4 designed for real-time, custom institutional interface which push up to 200 price update per second (not available on other APIs). It is their fastest and most popular solution. You will get full range of trading order types available at FIXAPI.cc.
In order to establish and maintain FIX connectivity, you must have an application that manages a network connection and which sends/receives FIX messages. An application that does this is referred to as a FIX engine. Today there are numerous commercial FIX engines as well as open-source alternatives, the most known of which is QuickFIX
FIXAPI.cc trading session reset weekly, it opens on Sundays between 5:00 PM ET and 5:15 PM ET. and closes on Fridays at 4:55 PM ET.