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…