title: How to integrate currency rate exchange Api in a WebApp (Nodejs)
body: <p>I'm trying to build a WebApp(for sending money) with React, Nodejs for a customer. Since it will be selling goods worldWide I have to integrate the currency exchange feature in it. After doing some research I found that for some reasons enumerated here <a href="https://stackoverflow.com/questions/58904245/should-api-fetching-be-frontend-or-backend">Choose backend for All the fetching logic</a> and also the choice of the API provider according to :</p>
  <ol>
  <li>API features: features of each of the currency APIs</li>
  <li>Data coverage: the number of currencies supported, data sources, frequency of updates, and other data coverage features of the APIs</li>
  <li>Price</li>
  <li>Ease of use.</li>
  </ol>
  <p>the main question is how do I integrate it? the cost of Some API depends on the number of requests, is smart to send a request for updating data every time a customer wants to do a transaction ? or do I send request from the backend that is not depending on the customer's transaction but save the data? if yes, what will be the good frequency? is there any free reliable API out there?</p>
  <p>Not code question. Would like to have the idea of how it works for getting currency rates  information, what is good update frequency, is there any good free out there but reliable</p>