The screenshot above is from a website that allows people to find infrastructure projects near them and gives them visibility into their purpose and cost. We were given the entire geospatial dataset in ArcGIS format, converted it to JSON, divided it into chunks, and exposed it through an API. I considered using R-trees or quadtrees for performance, but that ended up not being necessary.

I used OpenStreetMap to display the map, because we couldn't afford a Google Maps license. This ended up paying off, as we eventually had to customize the map rendering code to do things that would not have been possible with Google Maps.