title: Unset session after some time
body: <p>I am building a online ticket booking site . In this I am doing the following things : The user searches the bus with their seat numbers . The database is updated with the seat numbers with <code>temp_seat_book = 'Y'</code> . If he books the ticket paying money his status will be updated to <code>final_ticket_book = 'Y'</code> . Now I want to delete the field whose <code>temp_seat_book = 'Y'</code> but 
  <code>final_ticket_book = 'N'</code> . For this I need to delete the session_ids which is more than 10minutes old and <code>final_ticket_book = 'N'</code>. So how I can implement the background job?</p>