Yes, the data is fairly compact. Data for the entire world enough for rendering to zoom level 18 generally comes in under 35GB (give or take 10 GB depending on what features you need). If you need to got to zoom levels approaching ~18 then there is no way to do this with image tiles. Vector tiles are the more efficient way. More details on the encoding at https://github.com/mapbox/vector-tile-spec and the encoder at https://github.com/mapbox/mapnik-vector-tile