Why Facebook Images are Available After Deletion?

Facebook works on Continent Distribution Network known as CDN to give quick and easy access to its users. When an image and video is uploaded then many copies of same photo or video becomes available on local servers. When a user deletes a photo or video from his account then it is deleted from the Facebook’s main server but remains available on other server for 30 months (2.5 Years) and user’s can access deleted photo and video.