A new flyover opens. Which map tiles change?

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A new flyover opens. Every phone's map has to show it. So which tiles do you redraw? And how do you find them fast?

Google wrote in 2010: image tiles for the world, at 20 zoom levels? Over 360 billion. So it moved to vector tiles. Just the geometry, drawn on the phone. Over 100 times less data.

Now name each tile with a quadkey. One digit per zoom level. Zoom in, add a digit. 2130 is one of the four children of 213. Zoom out? Drop the last digit. That's the parent. No lookup at all.

So, the flyover. Its geometry lands in one zoom-16 tile. Plus that tile's 16 ancestors. Found by chopping one quadkey, digit by digit. The builder rebuilds only those. The rest of the world stays put.

Those 17 are rebuilt under a new map version. Nothing is overwritten in place. Phones fetch the new version's manifest. Then only the tiles that changed.

And the red and green traffic colours? Kept out of the base tiles. A tiny overlay that expires in about a minute. The base map caches for days.

Name tiles so a parent is just a shorter key. Then one flyover is 17 tiles to rebuild. Found without a single lookup.

Full breakdown in the lecture.