Making a tile when it is asked for is not new: vector tiles get built from a database per
request, raster tiles get cut out of Cloud-Optimized GeoTIFFs. But the expensive end stayed
baked. Terrain, and buildings as 3D Tiles, still arrive as pyramids somebody built in
advance — because the arithmetic is heavy, so it gets done ahead of time.

This talk is about three services that do that heavy work inside the request instead, on the
machines that serve a CDN: nothing baked, and no server kept alive.

Re:Earth Terrain and Re:Earth Buildings already work that way — global terrain, and the
world's buildings. Both are usable today: open source, no API key.

And once the drawing happens inside the request too, a map style no longer has to be a list
of rules — a brush can be picked, and a map painted on paper, at the moment someone asks for
it. The third service goes live during this talk.