Hmm, I'm curious about how much this is overstating the effectiveness of the optimizations in order to teach about them. With this approach, (it seems like) you would still have to render the highest zoom level first, which already takes 3/4 the render time anyway. There are lots of other optimizations you can do (and they probably are doing) there, but they aren't related to the tree/reference-based ones mentioned here.
The presentation also seems to overstate the redundancy found in the land tiles. You would get savings from water tiles at all zoom levels, which would be enormous, but (looking at http://mapbox.com/maps) even if humans only cover 1% of the land, our infrastructure is well enough distributed that it and inland water and other details they've included would preclude redundancy at all but the highest zoom levels (although, in this case, the highest zoom level taking up 3/4 of the tiles saves the most).
With that in mind, I'm wondering about the claimed rendering time of 4 days. That fits nicely with the story told, but with the 32 render servers mentioned at the end, that would seem to be 128 CPU days (though I'm not sure about the previous infrastructure they were comparing it to), which is actually close to the count mentioned early on with a super-optimized query and render process. This is all just supposition, so I don't want to sound too sure of myself, but the storage savings seems to be the big win here (60% from water + redundancy at highest zoom levels), while I would guess that you would save considerably less in processing (15% from water + minor redundancy on land (absent other optimizations e.g. run-length-based ones)).
The presentation also seems to overstate the redundancy found in the land tiles. You would get savings from water tiles at all zoom levels, which would be enormous, but (looking at http://mapbox.com/maps) even if humans only cover 1% of the land, our infrastructure is well enough distributed that it and inland water and other details they've included would preclude redundancy at all but the highest zoom levels (although, in this case, the highest zoom level taking up 3/4 of the tiles saves the most).
With that in mind, I'm wondering about the claimed rendering time of 4 days. That fits nicely with the story told, but with the 32 render servers mentioned at the end, that would seem to be 128 CPU days (though I'm not sure about the previous infrastructure they were comparing it to), which is actually close to the count mentioned early on with a super-optimized query and render process. This is all just supposition, so I don't want to sound too sure of myself, but the storage savings seems to be the big win here (60% from water + redundancy at highest zoom levels), while I would guess that you would save considerably less in processing (15% from water + minor redundancy on land (absent other optimizations e.g. run-length-based ones)).