How increase KML output performance?

Question

Hi How can I improve this KML generator? We discussed pre-generating the output like a cron job perhaps saving a blob to blobstore since it can't serve many markers like this. Can you recommend me how to proceed? Is the bottleneck where using images?

class KML(webapp.RequestHandler):#get max, make static or cron job save file like blob
     def get(self):            
        from django.template import defaultfilters
        start=datetime.datetime.now()-timedelta(days=150)#vary  
        host = os.environ.get("HTTP_HOST", os.environ["SERVER_NAME"])
        #count = 22        
        count = int(self.request.get('count')) if not self.request.get('count')=='' else 50
        a= A.all().filter("modified >", start).filter("published =", True).order("-modified").fetch(count)        
        self.response.out.write('<?xml version="1.0" encoding="UTF-8"?><kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom"&gt;&lt;Document&gt;')
        for a in a:           
            if a.geopt:  
                image = a.matched_images.get()
                if image:
                    imageid=image.key().id()   
                    kml = ('<Placemark><name></name><description><![CDATA[<img src="http://%s/images/%d.%s"&gt; %s ]]></description><Style><IconStyle><Icon><href>http://www.google.com/intl/en_us/mapfiles/ms/icons/green-dot.png&lt;/href&gt;&lt;/Icon&gt;&lt;/IconStyle&gt;&lt;/Style&gt;&lt;Point&gt;&lt;coordinates&gt;%d,%d&lt;/coordinates&gt;&lt;/Point&gt;&lt;/Placemark&gt;'
           ) %(host,image.key().id(),image.full_ext,'<a href="http://'+host+'/'+str(a.key().id())+'"&gt;'+a.title+'&lt;/a&gt;&lt;br/&gt;'+defaultfilters.urlize(  defaultfilters.truncatewords(  a.text , 20 )  ),a.geopt.lon,a.geopt.lat)
                else:  
                    kml = ('<Placemark><name></name><description><![CDATA[%s]]></description><Style><IconStyle><Icon><href>http://www.google.com/intl/en_us/mapfiles/ms/icons/green-dot.png&lt;/href&gt;&lt;/Icon&gt;&lt;/IconStyle&gt;&lt;/Style&gt; <Point><coordinates>%d,%d</coordinates></Point></Placemark>'
           ) %('<a href="http://'+host+'/'+str(a.key().id())+'"&gt;'+a.title+'&lt;/a&gt;&lt;br/&gt;'+defaultfilters.urlize(  defaultfilters.truncatewords( defaultfilters.striptags(  a.text ) , 20 )  ),a.geopt.lon,a.geopt.lat)
                self.response.out.write(kml)                
        self.response.out.write( '</Document></kml>')