What is &quot;latency arb&quot; then? To &quot;flip the spread&quot; you need to predict where the market will go after your order gets elected. The market is pretty efficient. The average limit order loses the spread and rebates after execution. You can&#x27;t make money just being on the bid and offer with the crowd without a directional prediction.<p>You are right that the actual execution algorithms aren&#x27;t doing super complex analysis in real-time. Usually that is done offline through simulation to generate rule sets, decision trees or factor weightings. That work is definitely quantitative. Aside from pure arbitrage, most HFT strategies have a statistical edge, not a mechanical one.