I work on low(ish) latency trading systems in FX. FIX is the standard communication protocol and familiarity with it is essential for me. Here you can look up the standard message types and tag values:
https://fiximate.fixtrading.org/
They also have docs for the standard message flows you can expect during trading. I use it regularly.
They also have docs for the standard message flows you can expect during trading. I use it regularly.