It's significant, especially when locality is related to temporal locality (ie: most reads will be relatively recent writes). The biggest upside is serving mor

It's significant, especially when locality is related to temporal locality (ie: most reads will be relatively recent writes). The biggest upside is serving more reads from the in memory portion of indexes after things start having to live on disk. Occasionally, locality also nets a win on relevant query results residing in contiguous storage blocks- but fast queries should be reading tons of data in the first place.