The European Space Agency's astrometry satellite Gaia was launched in December 2013 and started its scientific operations in July 2014 after an extended payload commissioning period. During the first year of the nominal mission the astrometric instrument alone has made around 250 Billion individual measurements which already now constitues one of the largest astronomical datasets in existence. Operations will continue for at least the next 4 years and after an extensive data processing effort an astronomical catalogue containing some 1.5 Billion celestial objects will be produced. We describe the chosen key concepts for handling the massive amounts of daily data at the Science Operations Centre at ESAC, Madrid, their initial processing and dissemination to the other five partner processing centres. We will also illustrate some of the great challenges that the mission data poses in terms of storage, processing, monitoring, and analysis.