From a price tick
to a paper trade.

The problem

A changing price is only one piece of a trading experience. Orders, balances, holdings and P&L need to stay connected as a person moves through the workflow.

How the parts connect

Finnhub and Fyers integrations feed a bounded market-data buffer that produces one-minute OHLCV candles. WebSocket updates follow authenticated clients and their symbol subscriptions. Express routes call services for trading and portfolios.

A deliberate choice

Simulated order execution groups balance, holding and transaction changes into SQLite transactions. A bounded history per symbol keeps the in-memory data buffer from growing without a limit.

Scope

PaperBull is a paper-trading project using virtual orders. It is not a brokerage, investment service or a claim of production trading reliability.