title: Best practice to display POI in iPhone's MapKit?
body: <p>Assuming I have a database of POI with their respective coordinates (longitude &amp; latitude). What would be the "standard" way to display the POI as annotations around the user's current location? To elaborate:</p>
  
  <ul>
  <li>Given a zoom level, I guess I have to search through the database for all POI whose distance to the current location &lt; a certain threshold, then create annotations for them. Or is there any smarter way?</li>
  <li>If the user zooms in/out, moves the map... I will need to redo the whole thing again?</li>
  <li>It seems that MapKit has a mechanism to cache/reuse annotations. Should I create a lot of them right away and let MapKit decides what to render when the visible region changes? I guess this would make the transition smoother, but also consumes more memory. What is your experience with this?</li>
  </ul>
  
  <p>Thanks.</p>