ImageKit plugs right into your existing infrastructure with minimal code changes (a mere DNS entry change if you use a CNAME).
Image request/response flow
Think of ImageKit as an image CDN. When a request leaves the browser, it hits our CDN. In 90% of the cases, the image is served from the CDN cache. In case the image is not there on CDN, then CDN internally requests our core-image processing servers.
We maintain a copy of processed images in our internal caches (in addition to CDN cache) and will first look up the image there. In case the image is found, we return the response to CDN, and all further requests are served from the CDN cache itself.
If the image is not found in our internal caches, we will download that image from your origin (as per the configuration in your account), do all the required processing, cache a copy and deliver it.