Mirage JS was built to give frontend developers the ability to simulate actual backend API calls. So far, we have seen how we can create records with Mirage, intercept API requests via route handlers and, last but not least, how the shape of the data returned to us from Mirage is affected. In this part of the series, we will see Mirage mechanism for simulating other aspects of an actual backend server like slow network, HTTP status code response, and also making requests to an actual backend even though Mirage is intercepting your frontend requests.

https://www.smashingmagazine.com/2020/06/mirage-javascript-timing-response-passthrough/