The document discusses the evolution of trading system architectures from traditional to automated. Traditionally, trading systems consisted of components to access market data, store historical data, analyze data, input trades, and route orders. With automation and high-frequency trading, latency had to be reduced to milliseconds requiring event processing and order generation to move to servers. Architectures now feature complex event processing engines, risk management checks, standardized FIX protocols, data normalization, order routing, extensive data storage, and replay capabilities for backtesting. Overall the document outlines how trading systems have been optimized for speed and automation to facilitate high-frequency algorithmic trading.