title: sorting relationships in a graph database by reverse chronological order
body: <p>suppose I'm making a social application whose data I store with a graph db, where entities (people, things...) are nodes (w/ property "name") and actions are relationships (w/ properties "what" and "when").
  also suppose huge db and high load so the implementation should not just work, it should be as fast as possible.</p>
  
  <p>how would you answer questions like "what happened in the last 5 minutes?" that list actions (and their subjects/objects) in reverse chronological order?</p>