The Twitter Image Pipeline is a streamlined framework for fetching and storing images in an application. The high-level concept is that all requests to fetch or store an image go through an image pipeline which encapsulates the work of checking the in-memory caches and an on disk cache before retrieving the image from over the network as well as keeping the caches both up to date and pruned. Twitter Image Pipeline came to fruition as numerous needs rose out of Twitter for iOS use cases. The...