Contrary to popular belief, the primary edge in HFT comes from exploiting the physical and regulatory structure of markets, not from discovering complex financial patterns. Speed is the main tool used for this structural exploitation, prioritizing infrastructure over algorithmic genius.

The head of AI at Hudson River Trading suggests the industry is moving past needing human-understandable narratives for trading strategies. If a model, after rigorous backtesting, finds a pattern that works, it's traded, even if the logic is incomprehensible or feels like a "loss of control" to humans.

The world's top investors have a median hit rate of only 49%, meaning they lose money on the majority of their investments. Their outperformance comes from making significantly more on their winners than they lose on their losers, a concept known as payoff ratio.

While seductive, complex trades with multiple conditions (knock-ins, knock-outs) create numerous ways for a core thesis to be correct on direction but still result in a loss. Simplicity in trade expression is a form of risk management that minimizes the pain of a good call being ruined by flawed execution.

High-frequency trading firms are expanding into medium-frequency horizons (days to weeks). They use their sophisticated short-term AI models, which can predict optimal prices within the next hour, to inform the execution strategy for their longer-term positions, creating a cascading effect where intraday precision enhances multi-day trading performance.

Successful investing isn't about being right all the time; it's about making your wins exponentially larger than your losses. Top investors like Paul Tudor Jones only enter trades where the potential reward is at least five times the risk, allowing them to be wrong often and still profit.

AI models can predict short-term stock prices, defying the efficient market hypothesis. However, the predictions are only marginally better than random, with an accuracy akin to "50.1%". The profitability comes not from magic, but from executing this tiny statistical edge millions of times across the market.

Instead of vaguely aiming to make "as much as we can," defining a specific, acceptable Return on Investment (ROI) is crucial. This discipline allows a trader to lock in that return and then focus on maximizing it through complex strategies on the curve, rather than simple speculation.

Much of HFT is a game between market makers and liquidity takers. When a related asset moves, makers race to cancel their now-mispriced ('stale') orders. Simultaneously, takers race to execute against those same orders. This core conflict is what fuels the arms race for speed.