@a.espolov: check the untangled videos, he demonstrates how to do optimistic updates and non-optimistic as well, I believe on this video (if not, check the others, all are great :)): https://www.youtube.com/watch?v=t49JYB27fv8&index=7&list=PLVi9lDx-4C_T_gsmBQ_2gztvk6h_Usw6R