Richard, have you ever read Flash Boys? It’s by the author of The Big Short and talks about the lengths hedge funds went to to get a competitive advantage in trading.
Some of the hedge funds actually moved their server a few feet closer to the exchange server. Consequently, the picosecond(?) difference in trading time allowed their computer to see their competitors trades and execute a trade, based on that intel, before their competitor’s trade was processed.
They’ve since put in trading hold controls to eliminate those unfair advantages, but the idea that a hedge fund could buy a stock in a fraction of a second and then turn around and sell it before the second was up still boggles my mind.