A backtest can look flawless and still be untradeable. I've watched rules with clean equity curves that assumed every signal filled at the closing print fall apart the moment real…
Pull up two market data feeds on the same stock at the same second and you'll often see them disagree. One shows 1,200 shares offered at 48.75. The other shows…
Picture a 5,000-share market order hitting a thin small-cap at 10:47 in the morning. The last trade printed at 24.10, so you'd expect a fill somewhere near there. Instead the…
You mark a small-cap you've been watching, the last trade printed at 24.05, and you send a market order to get in. The fill comes back at 24.18. Nothing moved…