TL;DR — Stock Trading Platform

Design a stock trading platform similar to Robinhood that allows retail investors to place buy and sell orders for stocks, ETFs, and options. The system must handle real-time market data feeds, maintain an order book for each security, execute trades through a matching engine, and ensure regulatory compliance with SEC and FINRA requirements. Key features: Place market, limit, and stop-loss orders for equities. Real-time order book display with bid/ask prices and depth.