How to design a crypto exchange app in Bubble

In API Connector, create an API called 'CoinGecko.' Add a GET call: https://api.coingecko.com/api/v3/simple/price?ids=[coin_ids]&vs_currencies=usd&include_24hr_change=true. Initialize with coin_ids = bitcoin,ethereum. This returns current prices and 24-hour change percentages.

1GET https://api.coingecko.com/api/v3/simple/price?ids=bitcoin,ethereum&vs_currencies=usd&include_24hr_change=true
2
3Response:
4{
5  "bitcoin": { "usd": 65432.10, "usd_24h_change": 2.35 },
6  "ethereum": { "usd": 3456.78, "usd_24h_change": -1.2 }
7}

Create a page with a market overview showing top cryptocurrencies. Use a Repeating Group displaying coin name, current price, 24h change (green for positive, red for negative), and a mini chart icon. Add a search and sort by name, price, or change. Clicking a coin opens the trading page for that pair.

On the trading page, build a two-tab form: Buy and Sell. Each tab has: amount input (number of coins), price display (current market price), total cost calculation (amount × price), and a Submit Order button. For demo purposes, the order workflow creates a Trade record: user, coin, type (buy/sell), amount, price, total, timestamp.

Add two sections: Order Book showing recent buy/sell orders from all users (Repeating Group of Trade records sorted by date, color-coded green for buys and red for sells), and Trade History showing the current user's past trades. Display each trade's coin, type, amount, price, and total.

Create a 'Holding' data type: user, coin_id (text), amount (number), avg_buy_price (number). When a buy order executes, update or create the Holding. Display a portfolio page with current values (amount × current API price), cost basis, and profit/loss. Add a pie chart showing portfolio allocation.