When building an application that deals with foreign exchange (FX) rates, selecting the right type of data is a foundational decision. Do you need the most current, up-to-the-second rate, or do you need a series of rates from last week, last month, or last year? The FinFeedAPI Currencies API provides two distinct endpoints to address these needs: one for real-time rates and another for historical data.
This guide will compare and contrast these two APIs, explain their specific use cases, and detail the calculation methodology behind the rates to help you choose the right data source for your project.
Currencies API FX Endpoints
Currencies API splits its currency exchange rate data across two specialized services:
- Real-time API:
https://api-realtime.fx.finfeedapi.com - Historical API:
https://api-historical.fx.finfeedapi.com
While they both provide exchange rates, their purpose and the nature of the data they return are quite different.
Understanding Real-Time FX Rates
The Real-time API is focused entirely on the present. Its purpose is to give you the most current available exchange rate for a currency pair.
Use Cases:
- Currency Converters: For applications that provide users with immediate currency conversions (e.g., "how much is 100 EUR in USD right now?"), the real-time endpoint is the correct choice.
- International E-commerce & Payment Gateways: When displaying prices in a local currency or processing an international transaction, you need the current rate to ensure accurate pricing for the customer.
- Live Price Tickers: Financial dashboards or mobile widgets that display the latest FX rates depend on a continuous feed of real-time data.
- Immediate Trading Decisions: Applications designed for manual or semi-automated trading might use real-time rates to inform immediate buy/sell decisions (though high-frequency trading bots often use even more direct data feeds).
Example Query: To get the current rate for Bitcoin to US Dollar, your application would make a GET request like this: GET /v1/exchangerate/BTC/USD
The response is a single, timestamped rate representing the most recent calculation.
Understanding Historical FX Rates
The Historical API, in contrast, is your window to the past. It allows you to retrieve exchange rates from a specific point in time or get a series of data points over a defined period.
Use Cases:
- Financial Charting and Analytics: To build a chart showing the performance of EUR/USD over the last year, you would use the historical API to fetch daily or hourly data points.
- Backtesting Trading Strategies: Algorithmic traders need historical data to test how their strategies would have performed under past market conditions. You can fetch minute-by-minute or even second-by-second data to simulate trades.
- Financial Modeling and Research: Economists and financial analysts use historical FX data to build predictive models, analyze currency correlations, and conduct academic research.
- Auditing and Record-Keeping: An application might need to record the exact exchange rate at the time of a past transaction. By querying the historical endpoint with a specific timestamp, you can retrieve that information.
Example Queries: To get the EUR/USD rate as it was at the beginning of 2023: GET /v1/exchangerate/EUR/USD?time=2023-01-01T00:00:00Z
To get a daily time series for EUR/USD for the first quarter of 2023: GET /v1/exchangerate/EUR/USD/history?period_id=1DAY&time_start=2023-01-01&time_end=2023-03-31
This endpoint returns data series, often in an Open, High, Low, Close (OHLC) format for each period, which is ideal for charting.
The VWAP-24H Calculation Methodology
A key aspect of FinFeedAPI's exchange rates is that they are typically calculated as a 24-hour Volume Weighted Average Price (VWAP-24H). This is not just a single last-trade price from one source; it's a more comprehensive and reliable figure.
Here's what that means for the data you receive:
- Volume-Weighted: The rate is an average of midpoint prices (the price between the best bid and ask), but prices from trades with higher volume have a greater impact on the average. This prevents small, insignificant trades from skewing the rate.
- Aggregated from High-Quality Sources: The API pulls data from multiple high-quality exchanges. It has an internal ranking system and prioritizes data from the most legitimate sources for any given currency pair.
- Stale Data is Discarded: To ensure freshness, any data point that hasn't been updated in the last 5 minutes is removed from the calculation.
- Robust to Outliers: For currency pairs with data from at least three exchanges, any rate that falls outside of a 3-sigma range (a statistical measure of deviation) is discarded. This helps to eliminate erroneous data points or anomalies from a single source.
The result is a more stable and representative exchange rate than you would get from a single tick on a single exchange, making it suitable for a wider range of financial applications that require reliability.
Which API Should You Use?
- For "what is the rate now?" scenarios, use the Real-time API. This includes any application where a user or system needs the current market value for a transaction or live display.
- For "what was the rate then?" or "what were the rates over this period?" scenarios, use the Historical API. This is your tool for analysis, backtesting, charting, and auditing past data.
By understanding the distinction between these two powerful APIs, you can build more efficient, accurate, and functional financial applications.
