title: REST API best practice - where to place a unique request identifier
body: <p>When designing a <code>REST API</code>, what is the best practice for adding a <code>unique request identifier</code> when performing an http request?</p>
  
  <p>I would normally add it in the headers as <code>x-request-id</code>, but today heard someone mention adding it in the url as a query string!</p>
  
  <p>Also after doing some research, it seems like some people add it in the response body and send it as part of the payload!</p>
  
  <p>Out of these three which would be the best application of a <code>unique request identifier</code> and why? What are the possible pros and cons of each approach?</p>