1. A computer-implemented method for indexing map data, the method comprising: from a set of trajectory points received from a global positioning system (GPS), determining, by one or more computer processors, whether each received trajectory point from the set of received trajectory points is associated with a road link of a map; building, by one or more processors, from the set of received trajectory points, a hybrid index, wherein the hybrid index comprises spatial cells, and wherein the spatial cells comprise a road link and a grid; receiving, by one or more processors, a query, wherein the query comprises an area of the map; responsive to determining that a received trajectory point from the set of received trajectory points is associated with a road link of the map, using the road link for a spatial cell; responsive to determining that a received trajectory point from the set of received trajectory points is not associated with a road link of the map, using the grid for the spatial cell; and displaying, by one or more processors, output data associated with the built hybrid index.