Requirements

Let's design a simplified stock exchange system. Imagine a bustling marketplace where buyers and sellers come together to trade stocks. Our system will manage stock orders, match compatible buy and sell orders, and track the state of the market. We need to carefully consider concurrency since multiple traders might be interacting with the system simultaneously. The system should handle different types of orders and be extensible to support new order types or trading strategies in the future. Order matching should be efficient and fair, simulating a real-world stock exchange. We'll also need to track trade executions and update stock prices accordingly. # Requirements ## Functional Requirements 1. **Stock Definition and Management:** * Define Stocks with attributes like symbol (e.g., "AAPL"), name (e.g., "Apple Inc."), and initial price. * Allow Stocks to be added to and removed from the exchange. 2. **Order Placement:** * Support different order types: * **Market Order:** Execute immediately at the best available price. * **Limit Order:** Execute only at a specified price or better. * **Stop-Loss Order:** Execute when the stock price reaches a specified stop price. * Allow specifying order quantity (number of shares). * Orders should have attributes like order ID, stock symbol, order type, quantity, price (if applicable), buy/sell side, and timestamp. 3. **Order Cancellation:** * Allow users to cancel pending orders. 4. **Order Matching:** * Implement a matching algorithm to match compatible buy and sell orders. Prioritize based on price and time of entry (FIFO within price level). * When a match is found, execute the trade. 5. **Trade Execution:** * Record all trade executions with details like stock symbol, quantity, price, buyer order ID, and seller order ID. * Update the last traded price of the stock. 6. **Market Data:** * Provide real-time market data for each stock, including: * Last Traded Price * Highest Bid Price * Lowest Ask Price * Order Book (list of open buy and sell orders at different price levels). A simplified order book is sufficient. 7. **Concurrency:** * Handle concurrent order placements, cancellations, and market data requests from multiple users. ## Non-Functional Requirements 1. **Thread Safety:** The system must be thread-safe to handle concurrent operations correctly. Pay close attention to shared data structures and potential race conditions. 2. **Extensibility:** The system should be designed to easily accommodate new order types, matching algorithms, and market data feeds without requiring major code changes. Consider the Open/Closed Principle. 3. **Modularity:** The system should be composed of loosely coupled modules with well-defined interfaces. This will improve maintainability and testability. 4. **Testability:** The system should be designed to be easily testable, with clear separation of concerns and the ability to mock dependencies. 5. **Efficiency:** Order matching should be performed efficiently. Consider data structures that facilitate fast lookups and matching. Algorithm choices should be appropriate for this real-time system. 6. **Real-time Updates:** Market data updates should be provided with minimal delay. Although precise latency numbers are not required, efficient data structures and algorithms should be chosen to minimize delays. 7. **Order Book Management:** Efficient storage and retrieval of orders within the order book is crucial. Consider using sorted data structures or other efficient techniques to maintain the order book's performance, especially during periods of high trading volume. 8. **Error Handling**: Consider handling scenarios such as invalid stock symbols, insufficient quantities, and price fluctuations. Provide meaningful error messages to users. ## Core Entities 1. **Stock:** Represents a stock traded on the exchange. Attributes: symbol, name, last traded price. 2. **Order:** Represents an order to buy or sell a stock. Attributes: order ID, stock symbol, order type, quantity, price (if applicable), buy/sell side, timestamp, status (e.g., PENDING, FILLED, CANCELLED). 3. **OrderBook:** Represents the order book for a specific stock. Contains lists of buy and sell orders at different price levels. 4. **Trade:** Represents a trade execution. Attributes: stock symbol, quantity, price, buyer order ID, seller order ID, timestamp. 5. **MatchingEngine:** Responsible for matching buy and sell orders. It could use strategies for different order types or matching algorithms. 6. **Exchange:** The main entry point for interacting with the stock exchange. Manages stocks, orders, and the matching engine.

Design a stock exchange system. There is a list of stocks given with following attributes

Requirements

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Functional Requirements

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Non-Functional Requirements

Core Entity Identification

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