The .glx file has a spatial index. Place positions are sorted in Hilbert order and grouped in blocks, and each block has a bounding box.
/v1/reverse reads the blocks whose boxes are within boundary.circle.radius kilometres of the point (default 1, at most 100). It returns the nearest places first, each with distance in kilometres.
layersandboundary.countryfilter the results.focus.point.latandfocus.point.lonare accepted and ignored.