How to Cache Exchange Rates and Avoid Rate Limit Errors

You integrated an exchange rate API, deployed to production, and then hit HTTP 429: Rate limit exceeded . This is the most common operational issue developers face with exchange rate APIs — and it is entirely preventable with proper caching. Why You Need to Cache Exchange Rates Exchange rates don't change every millisecond. Even "real-time" APIs like AllRatesToday update every 60 seconds. Fetching the same rate on every page load is wasteful and will quickly exhaust your quota. Consider a simple e-commerce site with 10,000 daily visitors: Without caching: 10,000 API calls/day = 300,000/month. You'll need a Large plan. With 5-minute cache: 288 API calls/day = 8,640/month. A Small plan covers it. With 1-hour cache: 24 API calls/day = 720/month. The Free tier is enough. The math: If your API updates every 60 seconds, caching for 5 minutes means you are at most 4 minutes behind — which is perfectly acceptable for price displays and most applications. Choosing Your Cache Duration (TTL) Use