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Stock Market Data Process Steps

1. Data Source Selection

Purpose: Identify and connect to an open-source provider of real-time US stock market data.

  • Options:
  • Yahoo Finance (via yfinance):
    • A popular open-source library that scrapes Yahoo Finance for real-time stock prices, historical data, and metadata.
    • While not an official API, it’s widely used and free.
  • Alpha Vantage:
    • Offers a free tier API with real-time and historical US stock data, including intraday prices (limited to 5 API calls per minute, 500 per day).
  • IEX Cloud (Free Tier):
    • Provides real-time US stock data via an open API, with a free plan offering up to 50,000 core messages monthly.
  • Polygon.io (Free Tier):
    • Delivers real-time stock data with a free plan (5-minute delay unless upgraded, but still useful for open-source setups).
  • Technical Steps:
  • Choose Provider:
    • Select IEX Cloud for this example due to its balance of real-time data and free access for US markets.
  • Register:
    • Sign up for a free API key on IEX Cloud’s website to access their endpoints.
  • Test Access:
    • Verify connectivity to endpoints like /stock/{symbol}/quote for live prices (e.g., AAPL, TSLA).
  • Outcome:
  • The app gains access to a reliable, open-source feed of US stock data.

2. Data Acquisition

Purpose: Fetch real-time stock data from the selected source for display and trading.

  • User Action:
  • Opens the Stock Market section or searches for a stock (e.g., "AAPL").
  • Technical Steps:
  • API Request:
    • The app’s backend service (market-service) sends a request to IEX Cloud’s real-time endpoint.
    • Example endpoint: GET https://cloud.iexapis.com/stable/stock/AAPL/quote?token=<your-api-key>
    • Data returned: Latest price, volume, high/low, etc.
  • Batch Requests:
    • For a market overview (e.g., S&P 500), use a batch endpoint to fetch multiple stocks efficiently.
    • Example: GET /stock/market/batch?symbols=AAPL,MSFT,GOOGL&types=quote
  • Frequency:
    • Poll the API every 5-15 seconds for real-time updates (adjust based on free tier limits).
  • Outcome:
  • Raw stock data (e.g., AAPL price: $150.25) is retrieved and ready for processing.

3. Data Processing

Purpose: Transform raw stock data into a usable format for the app.

  • Technical Steps:
  • Normalization:
    • Convert raw API responses into a consistent internal format (e.g., standardize fields like price, volume, timestamp).
  • Caching:
    • Store frequently accessed data in Redis to reduce API calls and improve performance (e.g., cache AAPL’s price for 5 seconds).
  • Aggregation:
    • For charts, process historical data (e.g., 1-minute intervals from IEX’s /stock/AAPL/chart/1m) into candlestick or line graph points.
  • Error Handling:
    • Handle rate limits or downtime by falling back to cached data or a secondary source (e.g., Yahoo Finance via yfinance).
  • Outcome:
  • Processed data is clean, cached, and optimized for display or trading logic.

4. Data Storage

Purpose: Retain stock data for historical analysis and compliance.

  • Technical Steps:
  • Short-Term Storage:
    • Keep real-time data in memory (Redis) with a TTL of 5-15 minutes for quick access.
  • Long-Term Storage:
    • Archive historical data in PostgreSQL for charts and audits.
    • Schema: Table stock_prices with columns symbol, price, volume, timestamp.
  • Retention Policy:
    • Store at least 6 years of trade-related data in AWS S3 to comply with SEC/FINRA regulations.
  • Outcome:
  • Data is available for immediate use and preserved for future needs.

5. Data Display

Purpose: Present real-time stock data to users in an intuitive interface.

  • User Action:
  • Views stock details, live prices, or charts in the app.
  • Technical Steps:
  • Push Updates:
    • Use WebSockets or server-sent events (SSE) to stream real-time prices from the backend to the front-end.
  • Render UI:
    • The front-end (e.g., React Native) displays:
      • Live price (e.g., "AAPL: $150.25").
      • Chart (e.g., lightweight library like Chart.js or Victory for mobile).
      • Additional metrics (volume, market cap).
  • Refresh:
    • Auto-update the UI every few seconds based on WebSocket/SSE data.
  • User Feedback:
  • Sees a dynamic, real-time view of stock prices and trends.