You should store the points in a singe column of datatype
Point which you can index with a
SPATIAL index (if your table type is
CREATE SPATIAL INDEX sx_place_location ON place (location)
Point($x - $radius, $y - $radius),
Point($x + $radius, $y + $radius)
AND Distance(Point($x, $y), location) <= $radius
This will drastically improve the speed of queries like "find all within a given radius".
Note that it is better to use plain
TM metrical coordinates (easting and northing) instead of polar (latitude and longitude). For small radii, they are accurate enough, and the calculations are simplified greatly. If all your points are in one hemishpere and are far from the poles, you can use a single central meridian.
You still can use polar coordinates of course, but the formulae for calculating the
MBR and the distance will be more complex.