current_time = datetime.utcnow()
response = HttpResponse()
last_modified = current_time - timedelta(days=1)
response['Content-Type'] = 'image/jpg'
response['Last-Modified'] = last_modified.strftime('%a, %d %b %Y %H:%M:%S GMT')
response['Expires'] = current_time + timedelta(days=30)
response['Cache-Control'] = 'public, max-age=315360000'
response['Date'] = current_time
response.content = image_content_blob
memcache.add(image_key, response, 86400)
return response
Images caching in browser - app-engine-patch aplication