How I Built and Monetized a Currency Exchange Rate API with FastAPI, Deployed it on Render, and Published it on RapidAPI.

dhritich20baruah Posted on May 30 How I Built and Monetized a Currency Exchange Rate API with FastAPI, Deployed it on Render, and Published it on RapidAPI. # python # fastapi # webdev # tutorial Introduction: In order to build passive income streams, I decided to publish APIs on RapidAPI. The idea is straightforward: build a useful API once, set up freemium pricing tiers, and earn recurring monthly income from subscribers. In this post we will see how I built a Currency Exchange Rate API using FastAPI and Python, deployed it on Render, and published it on RapidAPI. I'll walk through the entire process including a debugging issue that cost me a few hours and might save you the same frustration. The Tech Stack FastAPI — chose this over Flask and Express because it auto-generates interactive API documentation at /docs out of the box, which is extremely useful when setting up and testing endpoints before publishing Python — straightforward for API work, massive community support ExchangeRate-API — free data source providing live rates for 160+ currencies, no scraping needed Render — free tier hosting with simple GitHub deployment RapidAPI — marketplace where developers discover and subscribe to APIs The Three Endpoints # 1. Get latest rates for any base currency GET /latest?base=USD # 2. Convert between two currencies GET /convert?from=USD&to=INR&amount=100 # 3. List all supported currencies GET /currencies Enter fullscreen mode Exit fullscreen mode Here's the core conversion endpoint: @app.get ( " /convert " ) async def convert_currency ( from_currency : str = Query ( alias = " from " ), to_currency : str = Query ( alias = " to " ), amount : float = Query ( default = 1.0 ) ): from_currency = from_currency . upper () to_currency = to_currency . upper () async with httpx . AsyncClient () as client : response = await client . get ( f " { BASE_URL } /pair/ { from_currency } / { to_currency } / { amount } " ) data = response . json () return { " from " : from_curren