Update, communicated with the people at the geoswift library to implement the "prepared geometry" function of geos into the library. Implementation: Map the geometry of each of your features to a PreparedGeometry by calling the new makePrepared() method, and store those values somewhere alongside the original features/properties. At each location update use one of the new contains methods on PreparedGeometry to test for containment. https://github.com/GEOSwift/GEOSwift/pull/264

Is there anything documented about how to do this specifically?

Did you ever find a solution to this? Suffering a similar issue...