To provide a fair user experience, mobile app’s performance must be well tuned. Loads of work are invested into designing screens to provide fast feedback to end user and make 3rd party services communication as invisible as possible. There is unfortunately a wall, that mobile devs cannot go through – making faster external calls, especially in difficult environment like poor connection quality. But we – backend developers – can minimize that pain, but only as a result of tight cooperation.
Presentation contains a ton of knowledge about designing and developing mobile APIs and another ton of experience from the trenches.