Abstract: The Sirius Fast Orbit Feedback (FOFB) system entered operation for user beam in November 2022. It currently provides an improvement in the orbit stability relative to beam size from 20% to 2% in the vertical plane and from 5% to 1% in the horizontal plane, analyzed as RMS value integrated in a frequency band from 0.1 Hz to 1 kHz in out-of-the-loop BPMs. The target disturbance rejection crossover frequency of 1 kHz has been achieved in routine operation after a campaign of hardware, gateware and software debugging. The control loop has been analyzed and improved based on black box models obtained through system identification. This talk will describe the design principles that guided the project, the actual system architecture and implementation, the achieved results and interesting issues encountered along the journey from the design to commissioning and enhancements. It will be shown how the overall feedback loop delay was pushed down, how the system was built using hardware standards such as FMC and MicroTCA.4, both commercial and in-house developed open-source electronics. Strategies such as the use of a small number of BPM in the feedback loop, a modified scheme for the transferring the DC control effort cumulated in the fast corrects to the Slow Orbit Feedback System (SOFB) running in parallel and the employment of spatial filtering in the FOFB controller to avoid correction of orbit distortions caused by beam energy variations will be discussed. The overall system performance and the achieved orbit stability will be shown in further detail.