Seeking Feedback on Broker-Agnostic Trading Engine Design

Your design has a solid foundation, particularly with the broker adapter layer and a canonical internal data model. To maintain consistency among brokers, implementing a robust testing framework that simulates various broker behaviors can be helpful. For order state management, think about incorporating a state machine to manage intricate transitions. Containerization might also help avoid configuration drift, and it's vital to use the same execution pipeline for backtesting to ensure accuracy. Real-world conditions inevitably reveal flaws that testing might miss, so thorough stress testing and monitoring are essential.

You've already highlighted significant failure points in your challenges section. Not addressing these could lead to common pitfalls. Additionally, look into fill information for various order types, managing orders (like front-running and opposing orders), and issues specific to derivatives and OTC products. A major point of failure is designing a system that can withstand user errors — for instance, people might not always follow the correct sequence of operations. Your system needs to handle such scenarios smoothly to avoid breaking the data interaction.