Because Might Image uses your image source and using, we don't store original images on our servers. This has the benefit that you are always in control of the original.
However, to serve images at lighting speeds we rely heavily on caching and CDN. As a result, output images are stored in cache. This is the additional benefit that we don't put additional load on your image hosting when severing the original source image several times.
You can control caching settings and request cache purging via the dashboard or on the support page. More about caching can be found in our docs.