Facebook Developer Talks About The Engineering Behind Paper

In our push for polish we had a goal of never dropping a frame on high-end devices, and we mostly achieved that goal. The engineering complexity here is finding a way to fully utilize the multicore architecture of newer iPhones on top of the UIKit framework which has no support for multithreading. Significant work went into creating a framework for doing rendering work on multiple threads, and we spent a long time finding the balance between performance and complexity. Turning synchronous operations into asynchronous ones adds a lot of cognitive overhead, and this was one of the biggest challenges of the project.