The present disclosure relates to a first Web server (102, 204, 60, 70) and a second Web server (108, 214, 80, 90), and methods therein for controlling of a robot device over a cloud interface. A hyper-text transfer protocol, HTTP, request for a trajectory between a start position and a goal position is sent (S120, S230, 302, 402) towards the second Web server. One or more calculated trajectories are obtained (S122, 304) based on information as received encoded in the request. A HTTP response is sent (306) towards the first WEB server, comprising one or more calculated trajectories. Executing (S126, S266; 308, 406) of a trajectory at least based said one or more of the received trajectories is performed by the first Web server (102, 204, 60, 70). A scalable robot device control method is thus proposed, which is advantageously uses stored calculated trajectories between start and goal positions, for the robot device.