I am a doctoral candidate in joint supervision between the University of Tours and the École Polytechnique de Montréal. My thesis is supervised by Professor Louis-Martin Rousseau, Dr. Jorge E. Mendoza and Dr. Yannick Kergosien. It focuses on optimizing the problems of vehicle rounds in fast delivery. More specifically, I am interested in optimizing the picking process in e-commerce warehouses. These problems are characterized by a high rate of requests to be met in restricted time windows. My objective is to use the different mathematical tools (integer programming, constraint programming, heuristics, mathematicians, etc.) to propose efficient solutions allowing to organize the different routes of order pickers in such a way to satisfy customer demand.