Development of the atlas event picking server

During LHC Run 2, the ATLAS experiment collected almost 20 billion real data events and producedabout three times more simulated events. During physics analysis it is often necessary to retrieve oneor more events to inspect their properties in detail and check their reconstruction parameters.Occasionally it is also necessary to select larger samples of events in RAW format to reconstruct themwith enhanced code. The new Event Picking Server automates the procedure of finding the location ofthe events using the EventIndex and submitting the Grid jobs to retrieve the individual events from thefiles in which they are stored.