Mapbox certainly has been challenging. I read over a lot of code I found through GitHub search to figure out the overlays, and then went down a big rabbit hole

Mapbox certainly has been challenging. I read over a lot of code I found through GitHub search to figure out the overlays, and then went down a big rabbit hole trying to improve the rendering performance without much to show for it — I still think the way we render the overlays is a performance issue, but it could also be that Mapbox loads an entire webgl rendering engine with a lot of features we don't need. Longer term we'll probably move to OpenLayers + OpenStreetMap because Mapbox data is out of our budget by about 2 orders of magnitude.