CoachThe hot path of a trading system is the sequence of code executed between a triggering market event and the resulting order: the code whose duration is the tick-to-trade latency. Everything else (logging to disk, reporting, risk aggregation, configuration) runs off the hot path, on other threads or at other times.
Exemples
Example 1.4 (Light in fibre, bits on the wire)
A standard single-mode fibre has an effective group index of about 1.462 at a wavelength of 1 550 nm (a manufacturer’s specification sheet): light in it covers a metre in , so the 30 metres of cable between a server and an exchange’s switch inside one data centre cost about each way. Putting a frame on the wire takes its length in bits divided by the line rate, plus 20 bytes of preamble, start delimiter and inter-frame gap: a minimal 64-byte frame occupies a 10 Gb/s link for and a 25 Gb/s link for . A software path of a few microseconds is therefore dominated by computation and by the operating system, not by physics, until it is very good.